Air conditioner and indoor unit

ABSTRACT

An air conditioner includes: an outdoor unit; a liquid-refrigerant connection pipe and a gas-refrigerant connection pipe; an indoor unit; a gas-side shutoff valve; a refrigerant sensor; and a controller. The indoor unit is connected to the outdoor unit via the liquid-refrigerant and gas-refrigerant connection pipes, is arranged in an air-conditioning target space, and includes: an indoor heat exchanger that performs heat exchange between a refrigerant circulated between the indoor unit and the outdoor unit via the liquid-refrigerant and gas-refrigerant connection pipes and air sent to the air-conditioning target space; an indoor expansion valve that decompresses the refrigerant; a heat-exchange-side indoor liquid-refrigerant pipe that connects a liquid side of the indoor heat exchanger to the indoor expansion valve; and a connection-side indoor liquid-refrigerant pipe that connects the indoor expansion valve to the liquid-refrigerant connection pipe.

TECHNICAL FIELD

The present invention relates to air conditioners and indoor units, and more particularly relates to an air conditioner configured such that an outdoor unit and an indoor unit arranged in an air-conditioning target space are connected to each other via a liquid-refrigerant connection pipe and a gas-refrigerant connection pipe, and an indoor unit used for the air conditioner.

BACKGROUND

An existing air conditioner is configured such that an outdoor unit and an indoor unit arranged in an air-conditioning target space are connected to each other via a liquid-refrigerant connection pipe and a gas-refrigerant connection pipe. An example of such an air conditioner, as disclosed in PTL 1 (International Publication No. 2015/029160), performs two-phase refrigerant feed of decompressing a refrigerant to be brought into a gas-liquid two-phase state in an outdoor unit and then sending the refrigerant to an indoor unit via a liquid-refrigerant connection pipe. The air conditioner that performs the two-phase refrigerant feed can decrease the amount of refrigerant held by the entire air conditioner by the amount by which the refrigerant flowing through the liquid-refrigerant connection pipe turns into the gas-liquid two-phase state. The decrease in the amount of refrigerant can decrease the influence on environment in a case where the refrigerant leaks outside the air conditioner.

Although the amount of refrigerant held by the entire air conditioner is decreased to a certain degree by the two-phase refrigerant feed as disclosed in PTL 1, the decrease in the amount of refrigerant is not occasionally sufficient for the countermeasure to leakage of the refrigerant. This is because, when the refrigerant leaks from the indoor unit, the concentration of the refrigerant increases in the air-conditioning target space where the indoor unit involving leakage of the refrigerant is arranged, and the concentration may exceed its permissible value.

To address this, a shutoff valve may be added to each of both the liquid side and gas side of the indoor unit so as to isolate the indoor unit involving leakage of the refrigerant and to reduce leakage of the refrigerant into the air-conditioning target space.

Adding the shutoff valves to both the liquid side and gas side of the indoor unit, however, increases the cost, and further increases the size of the indoor unit if both the shutoff valves on the liquid side and gas side are arranged in the indoor unit.

According to one or more embodiments of the present invention, in an air conditioner configured such that an outdoor unit and an indoor unit arranged in an air-conditioning target space are connected to each other via a liquid-refrigerant connection pipe and a gas-refrigerant connection pipe as well as an indoor unit used for the air conditioner, increases in the cost and the size of the indoor unit are minimized and a refrigerant shutoff function when a refrigerant leaks from the indoor unit can be added.

PATENT LITERATURE PTL 1

International Publication No. 2015/029160

SUMMARY

An air conditioner according to one or more embodiments is an air conditioner including an outdoor unit, a liquid-refrigerant connection pipe and a gas-refrigerant connection pipe, an indoor unit, a gas-side shutoff valve, refrigerant leakage detecting means, and a control unit. The indoor unit is connected to the outdoor unit via the liquid-refrigerant connection pipe and the gas-refrigerant connection pipe, is arranged in an air-conditioning target space, and includes an indoor heat exchanger, an indoor expansion valve, a heat-exchange-side indoor liquid-refrigerant pipe, and a connection-side indoor liquid-refrigerant pipe. The indoor heat exchanger performs heat exchange between a refrigerant, which is circulated between the indoor unit and the outdoor unit via the liquid-refrigerant connection pipe and the gas-refrigerant connection pipe, and an air, which is sent to the air-conditioning target space. The indoor expansion valve decompresses the refrigerant. The heat-exchange-side indoor liquid-refrigerant pipe connects a liquid side of the indoor heat exchanger to the indoor expansion valve. The connection-side indoor liquid-refrigerant pipe connects the indoor expansion valve to the liquid-refrigerant connection pipe. The gas-side shutoff valve is connected to a gas side of the indoor heat exchanger. The refrigerant leakage detecting means detects leakage of the refrigerant. The refrigerant leakage detecting means may be a refrigerant sensor that directly detects the leaked refrigerant, or may be one that estimates the presence or amount of leaked refrigerant on the basis of the relationship between the temperature of the refrigerant in the indoor heat exchanger and the atmospheric temperature of the indoor heat exchanger. The indoor expansion valve is connected to the connection-side indoor liquid-refrigerant pipe by brazing. A brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe is provided with a coating material. The control unit causes the indoor expansion valve and the gas-side shutoff valve to be closed in accordance with information of the refrigerant leakage detecting means when the refrigerant leaks.

To add the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor unit, providing shutoff valves on both the liquid side and the gas side of the indoor unit may increase the cost and the size of the indoor unit. To minimize the increase in the cost and the size of the indoor unit, it is desirable to use the indoor expansion valve also as the shutoff valve on the liquid side for the situation in which the refrigerant leaks from the indoor unit.

In the indoor unit arranged in the air-conditioning target space, however, the connection-side indoor liquid-refrigerant pipe that connects the indoor expansion valve to the liquid-refrigerant connection pipe is connected to the indoor expansion valve by brazing. The brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe may corrode and the refrigerant may leak from the corroding portion. When the refrigerant leaks from the brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe, the refrigerant is continuously supplied from the liquid-refrigerant connection pipe to the brazing portion although the indoor expansion valve is closed to function as the shutoff valve on the liquid side of the indoor unit. The refrigerant may continuously leak from the indoor unit to the air-conditioning target space. Thus, it is difficult to use the indoor expansion valve also as the shutoff valve on the liquid side of the indoor unit unless such leakage of the refrigerant from the brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe is reduced.

In this case, by providing the coating material at the brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe as described above, leakage of the refrigerant from the brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe is reduced, and the indoor expansion valve can be used also as the shutoff valve on the liquid side of the indoor unit. As long as the indoor expansion valve can be used also as the shutoff valve on the liquid side of the indoor unit, the increase in the cost and the size of the indoor unit can be suppressed by that amount.

Accordingly, the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor unit can be added while the increase in the cost and the size of the indoor unit due to the provision of the shutoff valve on the liquid side of the indoor unit is reduced as much as possible.

For the coating material, any material can be employed as long as the material can suppress corrosion of the brazing portion. For example, a coating material made of resin can be employed. In particular, a water-repellent material and a heat-insulating material are suitable. For example, urethane resin can be employed.

In an air conditioner according to one or more embodiments, the connection-side indoor liquid-refrigerant pipe includes a first connection-side indoor liquid-refrigerant pipe connected to the indoor expansion valve, a second connection-side indoor liquid-refrigerant pipe connected to the liquid-refrigerant connection pipe, and a filter that is connected between the first connection-side indoor liquid-refrigerant pipe and the second connection-side indoor liquid-refrigerant pipe. The filter is connected to the first connection-side indoor liquid-refrigerant pipe and the second connection-side indoor liquid-refrigerant pipe by brazing. Brazing portions brazing the filter with the first connection-side indoor liquid-refrigerant pipe and the second connection-side indoor liquid-refrigerant pipe each are provided with a coating material.

In the indoor unit arranged in the air-conditioning target space, a filter may be provided to reduce inflow of foreign substances and so forth into the connection-side indoor liquid-refrigerant pipe and the indoor expansion valve. The filter is also connected to the connection-side indoor liquid-refrigerant pipe (the first connection-side indoor liquid-refrigerant pipe and the second connection-side indoor liquid-refrigerant pipe) by brazing. Due to this, the brazing portions brazing the filter with the first connection-side indoor liquid-refrigerant pipe and the second connection-side indoor liquid-refrigerant pipe may corrode and the refrigerant may leak from the corroding portions. This makes difficult to use the indoor expansion valve also as the shutoff valve on the liquid side of the indoor unit, like the brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe (the first connection-side indoor liquid-refrigerant pipe).

In this case, by providing the coating materials at the brazing portions brazing the filter with the first connection-side indoor liquid-refrigerant pipe and the second connection-side indoor liquid-refrigerant pipe as described above, leakage of the refrigerant from the brazing portions brazing the filter with the first connection-side indoor liquid-refrigerant pipe and the second connection-side indoor liquid-refrigerant pipe is reduced, and the indoor expansion valve can be used also as the shutoff valve on the liquid side of the indoor unit.

Even in the case where the filter is provided in the connection-side indoor liquid-refrigerant pipe, the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor unit can be added while the increase in the cost and the size of the indoor unit due to the provision of the shutoff valve on the liquid side of the indoor unit is reduced as much as possible.

For the coating material, any material can be employed as long as the material can suppress corrosion of the brazing portion. For example, a coating material made of resin can be employed. In particular, a water-repellent material and a heat-insulating material are suitable. For example, urethane resin can be employed.

In an air conditioner according to one or more embodiments, the outdoor unit includes an outdoor heat exchanger and a liquid-pressure adjustment expansion valve. When the refrigerant is sent from the outdoor heat exchanger to the indoor unit via the liquid-refrigerant connection pipe, the control unit controls the liquid-pressure adjustment expansion valve to decompress the refrigerant flowing through the liquid-refrigerant connection pipe to be brought into a gas-liquid two-phase state, and controls the indoor expansion valve to decompress the refrigerant decompressed by the liquid-pressure adjustment expansion valve.

Since the outdoor unit includes the liquid-pressure adjustment expansion valve as described above, the two-phase refrigerant feed of decompressing the refrigerant to be brought into the gas-liquid two-phase state in the outdoor unit and then sending the refrigerant to the indoor unit via the liquid-refrigerant connection pipe can be performed. Thus, the amount of refrigerant held by the entire air conditioner can be decreased by the amount by which the refrigerant flowing through the liquid-refrigerant connection pipe turns into the gas-liquid two-phase state through the two-phase refrigerant feed. However, although the amount of refrigerant held by the entire air conditioner can be decreased by a certain degree through the two-phase refrigerant feed, when the refrigerant leaks from the indoor unit, the concentration of the refrigerant increases in the air-conditioning target space where the indoor unit involving leakage of the refrigerant is arranged, and the concentration may exceed its permissible value. In such a case, the two-phase refrigerant feed is not occasionally sufficient for the countermeasure to leakage of the refrigerant.

In this case, by providing the coating material at the brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe as described above, leakage of the refrigerant from the brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe is reduced, and the indoor expansion valve can be used also as the shutoff valve on the liquid side of the indoor unit.

Accordingly, even in the case where the two-phase refrigerant feed is not sufficient for the countermeasure to leakage of the refrigerant, the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor unit can be added while the increase in the cost and the size of the indoor unit due to the provision of the shutoff valve on the liquid side of the indoor unit is reduced as much as possible. The addition of the refrigerant shutoff function makes the countermeasure to leakage of the refrigerant sufficient.

In an air conditioner according to one or more embodiments, the indoor unit includes a plurality of the indoor units, and the gas-side shutoff valve is provided to correspond to each of the indoor units.

In this case, the plurality of indoor units and the plurality of gas-side shutoff valves are provided as described above. Even with this configuration, the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor units can be added while the increase in the cost and the sizes of the indoor units due to the provision of the shutoff valves on the liquid sides of the indoor units is reduced as much as possible.

In an air conditioner according to one or more embodiments, the control unit causes only the indoor expansion valve and the gas-side shutoff valve corresponding to the indoor unit in which the refrigerant leaks among the plurality of indoor units to be closed in accordance with information of the refrigerant leakage detecting means when the refrigerant leaks.

In this case, when the refrigerant leaks from the indoor unit, only the indoor unit in which the refrigerant leaks can be isolated as described above.

Accordingly, the indoor unit in which the refrigerant does not leak can continue the operation.

In an air conditioner according to one or more embodiments, the gas-refrigerant connection pipe is provided with an external shutoff valve unit including the gas-side shutoff valve.

In this case, since the gas-side shutoff valve is arranged outside the indoor unit as described above, the increase in the size of the indoor unit can be suppressed.

In an air conditioner according to one or more embodiments, the gas-side shutoff valve is connected, by brazing, to an indoor-side gas connection pipe that is connected to a portion of the gas-refrigerant connection pipe on a side of the indoor unit, and an outdoor-side gas connection pipe that is connected to a portion of the gas-refrigerant connection pipe on a side of the outdoor unit. A brazing portion brazing the gas-side shutoff valve and the outdoor-side gas connection pipe is also provided with a coating material.

In the external shutoff valve unit, the gas-side shutoff valve is connected to the gas connection pipe connected to the gas-refrigerant connection pipe (the indoor-side gas connection pipe and the outdoor-side gas connection pipe) by brazing. Due to this, the brazing portion brazing the gas-side shutoff valve and the outdoor-side gas connection pipe may corrode and the refrigerant may leak from the corroding portion. In contrast, when the external shutoff valve unit is arranged in the air-conditioning target space together with the indoor unit, if the refrigerant leaks from the brazing portion brazing the gas-side shutoff valve and the outdoor-side gas connection pipe, the refrigerant is continuously supplied from the gas-refrigerant connection pipe to the brazing portion although the gas-side shutoff valve is closed, and the refrigerant may continuously leak from the external shutoff valve unit to the air-conditioning target space. Thus, it is required to reduce leakage of the refrigerant from the brazing portion brazing the gas-side shutoff valve and the outdoor-side gas connection pipe.

In this case, since the brazing portion brazing the gas-side shutoff valve and the outdoor-side gas connection pipe is provided with the coating material as described above, leakage of the refrigerant from the brazing portion brazing the gas-side shutoff valve and the outdoor-side gas connection pipe is reduced, and the external shutoff valve unit can be arranged in the air-conditioning target space together with the indoor unit.

Accordingly, the degree of freedom is ensured for arrangement of the external shutoff valve unit.

For the coating material, any material can be employed as long as the material can suppress corrosion of the brazing portion. For example, a coating material made of resin can be employed. In particular, a water-repellent material and a heat-insulating material are suitable. For example, urethane resin can be employed.

In an air conditioner according to one or more embodiments, the gas-refrigerant connection pipe is provided with a relay unit including a cooling/heating switching valve that individually switches corresponding one of the plurality of indoor heat exchangers to function as an evaporator or a radiator of the refrigerant. The control unit causes the indoor expansion valve and the cooling/heating switching valve serving as the gas-side shutoff valve to be closed in accordance with information of the refrigerant leakage detecting means when the refrigerant leaks.

In this case, as described above, the cooling/heating switching valve of the relay unit used for individually switching the operating state of corresponding one of the indoor units (that is, the state in which the indoor heat exchanger functions as the evaporator of the refrigerant and the state in which the indoor heat exchanger functions as the radiator of the refrigerant) is used also as the gas-side shutoff valve. As long as the cooling/heating switching valve can be used also as the shutoff valve on the gas side of the indoor unit, the increase in the cost and the size of the indoor unit can be suppressed by that amount.

Accordingly, the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor unit can be added while the increase in the cost and the size of the indoor unit due to the provision of the shutoff valve on the gas side of the indoor unit is reduced as much as possible.

In an air conditioner according to one or more embodiments, the cooling/heating switching valve is connected, by brazing, to an indoor-side gas connection pipe that is connected to a portion of the gas-refrigerant connection pipe on a side of the indoor unit, and an outdoor-side gas connection pipe that is connected to a portion of the gas-refrigerant connection pipe on a side of the outdoor unit. A brazing portion brazing the cooling/heating switching valve and the outdoor-side gas connection pipe is also provided with a coating material.

In the relay unit, the cooling/heating switching valve is connected to the gas connection pipe connected to the gas-refrigerant connection pipe (the indoor-side gas connection pipe and the outdoor-side gas connection pipe) by brazing. Due to this, when the relay unit is arranged in the air-conditioning target space together with the indoor unit, the brazing portion brazing the cooling/heating switching valve and the outdoor-side gas connection pipe may corrode and the refrigerant may leak from the corroding portion. In this case, when the relay unit is arranged in the air-conditioning target space together with the indoor unit, if the refrigerant leaks from the brazing portion brazing the cooling/heating switching valve and the outdoor-side gas connection pipe, the refrigerant is continuously supplied from the gas-refrigerant connection pipe to the brazing portion although the cooling/heating switching valve is closed, and the refrigerant may continuously leak from the relay unit to the air-conditioning target space. Thus, it is required to reduce leakage of the refrigerant from the brazing portion brazing the cooling/heating switching valve and the outdoor-side gas connection pipe.

In this case, since the brazing portion brazing the cooling/heating switching valve and the outdoor-side gas connection pipe is provided with the coating material as described above, leakage of the refrigerant from the brazing portion brazing the cooling/heating switching valve and the outdoor-side gas connection pipe is reduced, and the relay unit can be arranged in the air-conditioning target space together with the indoor unit.

Accordingly, the degree of freedom is ensured for arrangement of the relay unit.

For the coating material, any material can be employed as long as the material can suppress corrosion of the brazing portion. For example, a coating material made of resin can be employed. In particular, a water-repellent material and a heat-insulating material are suitable. For example, urethane resin can be employed.

In an air conditioner according to one or more embodiments, the gas-side shutoff valve is provided in the indoor unit. The indoor unit includes a heat-exchange-side indoor gas-refrigerant pipe that connects the gas side of the indoor heat exchanger to the gas-side shutoff valve, and a connection-side indoor gas-refrigerant pipe that connects the gas-side shutoff valve to the gas-refrigerant connection pipe. The gas-side shutoff valve is connected to the connection-side indoor gas-refrigerant pipe by brazing. A brazing portion brazing the gas-side shutoff valve and the connection-side indoor gas-refrigerant pipe is also provided with a coating material.

To add the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor unit, the indoor expansion valve of the indoor unit may be used also as the liquid-side shutoff valve, and the gas-side shutoff valve may be provided at the indoor unit. In this case, the connection-side indoor gas-refrigerant pipe that connects the gas-side shutoff valve to the gas-refrigerant connection pipe is connected to the gas-side shutoff valve by brazing. Due to this, the brazing portion brazing the gas-side shutoff valve and the connection-side indoor gas-refrigerant pipe may corrode and the refrigerant may leak from the corroding portion. When the refrigerant leaks from the brazing portion brazing the gas-side shutoff valve and the connection-side indoor gas-refrigerant pipe, the refrigerant is continuously supplied from the gas-refrigerant connection pipe to the brazing portion although the gas-side shutoff valve is closed. The refrigerant may continuously leak from the indoor unit to the air-conditioning target space. Thus, it is required to reduce leakage of the refrigerant from the brazing portion brazing the gas-side shutoff valve and the connection-side indoor gas-refrigerant pipe.

In this case, since the brazing portion brazing the gas-side shutoff valve and the connection-side indoor gas-refrigerant pipe is provided with the coating material as described above, leakage of the refrigerant from the brazing portion brazing the gas-side shutoff valve and the connection-side indoor gas-refrigerant pipe is reduced.

Accordingly, the shutoff valve provided in the indoor unit is provided on only the gas side, and the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor unit can be added.

For the coating material, any material can be employed as long as the material can suppress corrosion of the brazing portion. For example, a coating material made of resin can be employed. In particular, a water-repellent material and a heat-insulating material are suitable. For example, urethane resin can be employed.

An indoor unit according to one or more embodiments is an indoor unit connected to an outdoor unit via a liquid-refrigerant connection pipe and a gas-refrigerant connection pipe, arranged in an air-conditioning target space, and including an indoor heat exchanger, an indoor expansion valve, a heat-exchange-side indoor liquid-refrigerant pipe, and a connection-side indoor liquid-refrigerant pipe. The indoor heat exchanger performs heat exchange between a refrigerant, which is circulated between the indoor unit and the outdoor unit via the liquid-refrigerant connection pipe and the gas-refrigerant connection pipe, and an air, which is sent to the air-conditioning target space. The indoor expansion valve decompresses the refrigerant. The heat-exchange-side indoor liquid-refrigerant pipe connects a liquid side of the indoor heat exchanger to the indoor expansion valve. The connection-side indoor liquid-refrigerant pipe connects the indoor expansion valve to the liquid-refrigerant connection pipe. The indoor expansion valve is connected to the connection-side indoor liquid-refrigerant pipe by brazing. A brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe is provided with a coating material.

To add the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor unit, providing shutoff valves on both the liquid side and the gas side of the indoor unit may increase the cost and the size of the indoor unit. To minimize the increase in the cost and the size of the indoor unit, it is desirable to use the indoor expansion valve also as a shutoff valve on the liquid side for the situation in which the refrigerant leaks from the indoor unit.

In the indoor unit arranged in the air-conditioning target space, however, the connection-side indoor liquid-refrigerant pipe that connects the indoor expansion valve to the liquid-refrigerant connection pipe is connected to the indoor expansion valve by brazing. The brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe may corrode and the refrigerant may leak from the corroding portion. When the refrigerant leaks from the brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe, the refrigerant is continuously supplied from the liquid-refrigerant connection pipe to the brazing portion although the indoor expansion valve is closed to function as the shutoff valve on the liquid side of the indoor unit. The refrigerant may continuously leak from the indoor unit to the air-conditioning target space. Thus, it is difficult to use the indoor expansion valve also as the shutoff valve on the liquid side of the indoor unit unless such leakage of the refrigerant from the brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe is reduced.

In this case, by providing the coating material at the brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe as described above, leakage of the refrigerant from the brazing portion brazing the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe is reduced, and the indoor expansion valve can be used also as the shutoff valve on the liquid side of the indoor unit. As long as the indoor expansion valve can be used also as the shutoff valve on the liquid side of the indoor unit, the increase in the cost and the size of the indoor unit can be suppressed by that amount.

Accordingly, the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor unit can be added while the increase in the cost and the size of the indoor unit due to the provision of the shutoff valve on the liquid side of the indoor unit is reduced as much as possible.

For the coating material, any material can be employed as long as the material can suppress corrosion of the brazing portion. For example, a coating material made of resin can be employed. In particular, a water-repellent material and a heat-insulating material are suitable. For example, urethane resin can be employed.

An indoor unit according to one or more embodiments further includes a gas-side shutoff valve that is connected to a gas side of the indoor heat exchanger; a heat-exchange-side indoor gas-refrigerant pipe that connects the gas side of the indoor heat exchanger to the gas-side shutoff valve; and a connection-side indoor gas-refrigerant pipe that connects the gas-side shutoff valve to the gas-refrigerant connection pipe. The gas-side shutoff valve is connected to the connection-side indoor gas-refrigerant pipe by brazing. A brazing portion brazing the gas-side shutoff valve and the connection-side indoor gas-refrigerant pipe is also provided with a coating material.

To add the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor unit, the indoor expansion valve of the indoor unit may be used also as the liquid-side shutoff valve, and the gas-side shutoff valve may be provided at the indoor unit. In this case, the connection-side indoor gas-refrigerant pipe that connects the gas-side shutoff valve to the gas-refrigerant connection pipe is connected to the gas-side shutoff valve by brazing. Due to this, the brazing portion brazing the gas-side shutoff valve and the connection-side indoor gas-refrigerant pipe may corrode and the refrigerant may leak from the corroding portion. When the refrigerant leaks from the brazing portion brazing the gas-side shutoff valve and the connection-side indoor gas-refrigerant pipe, the refrigerant is continuously supplied from the gas-refrigerant connection pipe to the brazing portion although the gas-side shutoff valve is closed. The refrigerant may continuously leak from the indoor unit to the air-conditioning target space. Thus, it is required to reduce leakage of the refrigerant from the brazing portion brazing the gas-side shutoff valve and the connection-side indoor gas-refrigerant pipe.

In this case, since the brazing portion brazing the gas-side shutoff valve and the connection-side indoor gas-refrigerant pipe is provided with the coating material as described above, leakage of the refrigerant from the brazing portion brazing the gas-side shutoff valve and the connection-side indoor gas-refrigerant pipe is reduced.

Accordingly, the shutoff valve provided in the indoor unit is provided on only the gas side, and the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor unit can be added.

For the coating material, any material can be employed as long as the material can suppress corrosion of the brazing portion. For example, a coating material made of resin can be employed. In particular, a water-repellent material and a heat-insulating material are suitable. For example, urethane resin can be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of an air conditioner according to one or more embodiments of the present invention.

FIG. 2 illustrates a refrigerant system in the periphery of an indoor unit and an external shutoff valve unit constituting the air conditioner according to one or more embodiments of the present invention.

FIG. 3 is a flowchart of an operation when a refrigerant leaks in the air conditioner according to one or more embodiments of the present invention.

FIG. 4 illustrates a refrigerant system in the periphery of an indoor unit and an external shutoff valve unit constituting an air conditioner according to one or more embodiments of the present invention.

FIG. 5 illustrates a refrigerant system in the periphery of an indoor unit and an external shutoff valve unit constituting an air conditioner according to one or more embodiments of the present invention.

FIG. 6 is a schematic configuration diagram of an air conditioner according to one or more embodiments of the present invention.

FIG. 7 illustrates a refrigerant system in the periphery of an indoor unit constituting the air conditioner according to one or more embodiments of the present invention.

FIG. 8 is a flowchart of an operation when a refrigerant leaks in an air conditioner according to one or more embodiments of the present invention.

FIG. 9 is a schematic configuration diagram of an air conditioner according to one or more embodiments of the present invention.

FIG. 10 illustrates a refrigerant system in the periphery of an indoor unit and a relay unit constituting the air conditioner according to one or more embodiments of the present invention.

FIG. 11 is a flowchart of an operation when a refrigerant leaks in the air conditioner according to one or more embodiments of the present invention.

FIG. 12 illustrates a refrigerant system in the periphery of an indoor unit and a relay unit constituting an air conditioner according to one or more embodiments of the present invention.

FIG. 13 illustrates a refrigerant system in the periphery of an indoor unit and a relay unit constituting an air conditioner according to one or more embodiments of the present invention.

FIG. 14 is a flowchart of an operation when a refrigerant leaks in an air conditioner according to one or more embodiments of the present invention.

DETAILED DESCRIPTION

An air conditioner and an indoor unit used for the air conditioner according to one or more embodiments of the present invention are described below with reference to the drawings. It is to be noted that specific configurations of an air conditioner and an indoor unit used for the air conditioner according to one or more embodiments of the present invention are not limited to those of the following embodiments and their modifications, and may be modified within the scope of the gist of the disclosure.

Configuration

FIG. 1 is a schematic configuration diagram of an air conditioner 1 according to one or more embodiments of the present invention. FIG. 2 illustrates a refrigerant system in the periphery of indoor units 3 a and 3 b and external shutoff valve units 4 a and 4 b constituting the air conditioner 1 according to one or more embodiments of the present invention.

The air conditioner 1 is an apparatus that performs air conditioning (cooling and heating) in an air-conditioning target space in a building or the like through a vapor compression refrigeration cycle. The air conditioner 1 mainly includes an outdoor unit 2; a plurality of (in this case, two) indoor units 3 a and 3 b mutually connected in parallel; a liquid-refrigerant connection pipe 5 and a gas-refrigerant connection pipe 6 that connect the outdoor unit 2 to the indoor units 3 a and 3 b; a plurality of (in this case, two) external shutoff valve units 4 a and 4 b provided at the gas-refrigerant connection pipe 5; and a control unit 19 that controls components of the outdoor unit 2, the indoor units 3 a and 3 b, and the external shutoff valve units 4 a and 4 b. A vapor compression refrigerant circuit 10 of the air conditioner 1 is constituted by connecting the outdoor unit 2, the plurality of indoor units 3 a and 3 b, and the plurality of external shutoff valve units 4 a and 4 b to one another via the liquid-refrigerant connection pipe 5 and the gas-refrigerant connection pipe 6. The refrigerant circuit 10 is filled with a refrigerant such as R32.

Connection Pipe

The liquid-refrigerant connection pipe 5 mainly includes a joint pipe portion extending from the outdoor unit 2, and branch pipe portions 5 a and 5 b branched at a position before the indoor units 3 a and 3 b into a plurality of (in this case, two) pipe portions. The gas-refrigerant connection pipe 6 mainly includes a joint pipe portion extending from the outdoor unit 2, first branch pipe portions 6 a and 6 b branched at a position before the indoor units 3 a and 3 b into a plurality of (in this case, two) pipe portions, and second branch pipe portions 6 aa and 6 bb that connect the external shutoff valve units 4 a and 4 b to the indoor units 3 a and 3 b.

Indoor Unit

The indoor units 3 a and 3 b are arranged in air-conditioning target spaces in a building or the like. Being “arranged in air-conditioning target spaces” includes a situation in which the indoor units 3 a and 3 b are installed in the air-conditioning target spaces and a situation in which the indoor units 3 a and 3 b are not arranged in the air-conditioning target spaces but the indoor units 3 a and 3 b are connected to the air-conditioning target spaces via air ducts or the like. The indoor units 3 a and 3 b are connected to the outdoor unit 2 via the liquid-refrigerant connection pipe 5, the gas-refrigerant connection pipe 6, and the external shutoff valve units 4 a and 4 b, and constitute part of the refrigerant circuit 10 as described above.

Configurations of the indoor units 3 a and 3 b are described next. The indoor unit 3 a and the indoor unit 3 b have configurations similar to each other. Hence only the configuration of the indoor unit 3 a is described. For the configuration of the indoor unit 3 b, the description of the components of the indoor unit 3 b is omitted while an index “b” is applied to each component instead of the index “a” indicating each component of the indoor unit 3 a.

The indoor unit 3 a mainly includes an indoor expansion valve 51 a and an indoor heat exchanger 52 a. In addition, the indoor unit 3 a includes an indoor liquid-refrigerant pipe 53 a that connects the liquid side of the indoor heat exchanger 52 a to the liquid-refrigerant connection pipe 5 (in this case, the branch pipe portion 5 a), and an indoor gas-refrigerant pipe 54 a that connects the gas side of the indoor heat exchanger 52 a to the gas-refrigerant connection pipe 6 (in this case, the second branch pipe portion 6 aa).

The indoor expansion valve 51 a is an electric expansion valve that decompresses the refrigerant. The indoor expansion valve 51 a is provided in the indoor liquid-refrigerant pipe 53 a.

The indoor heat exchanger 52 a is a heat exchanger that performs heat exchange between the refrigerant, which is circulated between the indoor unit 3 a and the outdoor unit 2 via the liquid-refrigerant connection pipe 5 and the gas-refrigerant connection pipe 6, and the indoor air, which is sent to the air-conditioning target space. The indoor unit 3 a includes an indoor fan 55 a that sucks the indoor air into the indoor unit 3 a, that causes the indoor air to exchange heat with the refrigerant in the indoor heat exchanger 52 a, and then that sends the indoor air into the air-conditioning target space. That is, the indoor unit 3 a includes the indoor fan 55 a as a fan that sends the indoor air, which serves as a cooling source or a heating source of the refrigerant flowing through the indoor heat exchanger 52 a, to the indoor heat exchanger 52 a. The indoor fan 55 a is driven by an indoor fan motor 56 a.

The indoor liquid-refrigerant pipe 53 a mainly includes a heat-exchange-side indoor liquid-refrigerant pipe 71 a that connects the liquid side of the indoor heat exchanger 52 a to the indoor expansion valve 51 a, and a connection-side indoor liquid-refrigerant pipe 72 a that connects the indoor expansion valve 51 a to the liquid-refrigerant connection pipe 5 (in this case, the branch pipe portion 5 a). The liquid side of the indoor heat exchanger 52 a is connected to the heat-exchange-side indoor liquid-refrigerant pipe 71 a by brazing. The heat-exchange-side indoor liquid-refrigerant pipe 71 a is connected to the indoor expansion valve 51 a by brazing (the brazing portion is referred to as brazing portion 81 a). The indoor expansion valve 51 a is connected to the connection-side indoor liquid-refrigerant pipe 72 a by brazing (the brazing portion is referred to as brazing portion 82 a). The connection-side indoor liquid-refrigerant pipe 72 a is connected to the liquid-refrigerant connection pipe 5 (in this case, the branch pipe portion 5 a) by mechanical pipe joint, such as flare connection (the portion of the mechanical pipe joint is referred to as pipe joint portion 83 a). The pipe joint portion 83 a is connected to the connection-side indoor liquid-refrigerant pipe 72 a by brazing (the brazing portion is referred to as brazing portion 83 aa). Although not illustrated here, the connection-side indoor liquid-refrigerant pipe 72 a may be directly connected to the liquid-refrigerant connection pipe 5 (in this case, the branch pipe portion 5 a) by brazing without the mechanical pipe joint such as the pipe joint portion 83 a.

The brazing portion 82 a brazing the indoor expansion valve 51 a and the connection-side indoor liquid-refrigerant pipe 72 a is provided with a coating material 11 a. For the coating material 11 a, any material can be employed as long as the material can suppress corrosion of the brazing portion 82 a. For example, a coating material made of resin can be employed. In particular, a water-repellent material and a heat-insulating material are suitable. For example, urethane resin can be employed. The coating material 11 a may be provided at the brazing portion 82 a, or may be also provided at a portion other than the brazing portion 82 a. For example, as illustrated in FIG. 2, the coating material 11 a may be provided in a range from the indoor expansion valve 51 a to the pipe joint portion 83 a of the connection-side indoor liquid-refrigerant pipe 72 a (that is, so as to include the brazing portion 82 a and the brazing portion 83 aa). When the connection-side indoor liquid-refrigerant pipe 72 a is directly connected to the liquid-refrigerant connection pipe 5 (in this case, the branch pipe portion 5 a) by brazing, the coating material 11 a may be provided in a range from the indoor expansion valve 51 a to the brazing portion brazing the connection-side indoor liquid-refrigerant pipe 72 a and the liquid-refrigerant connection pipe 5 (in this case, the branch pipe portion 5 a).

The gas side of the indoor heat exchanger 52 a is connected to the indoor gas-refrigerant pipe 54 a by brazing. The indoor gas-refrigerant pipe 54 a is connected to the gas-refrigerant connection pipe 6 (in this case, the second branch pipe portion 6 aa) by mechanical pipe joint, such as flare connection (the portion of the mechanical pipe joint is referred to as pipe joint portion 84 a). The pipe joint portion 84 a is connected to the indoor gas-refrigerant pipe 54 a by brazing (the brazing portion is referred to as brazing portion 84 aa). Although not illustrated here, the indoor gas-refrigerant pipe 54 a may be directly connected to the gas-refrigerant connection pipe 6 (in this case, the second branch pipe portion 6 aa) by brazing.

The indoor unit 3 a is provided with a refrigerant sensor 57 a serving as refrigerant leakage detecting means for detecting leakage of the refrigerant. The refrigerant sensor 57 a is provided in the indoor unit 3 a in this case; however, it is not limited thereto. The refrigerant sensor 57 a may be provided, for example, at a remote controller for operating the indoor unit 3 a, or in the air-conditioning target space where the indoor unit 3 a is arranged. The refrigerant leakage detecting means may be the refrigerant sensor 57 a that directly detects the leaked refrigerant as described above, or alternatively, although it is not employed in this case, the refrigerant leakage detecting means may be one that estimates the presence or amount of leaked refrigerant on the basis of the relationship between the temperature of the refrigerant in the indoor heat exchanger 52 a and the atmospheric temperature of the indoor heat exchanger 52 a.

Outdoor Unit

The outdoor unit 2 is arranged outside the air-conditioning target space or outside the building or the like. The outdoor unit 2 is connected to the indoor units 3 a and 3 b via the liquid-refrigerant connection pipe 5, the gas-refrigerant connection pipe 6, and the external shutoff valve units 4 a and 4 b, and constitutes part of the refrigerant circuit 10 as described above.

A configuration of the outdoor unit 2 is described next.

The outdoor unit 2 mainly includes a compressor 21 and an outdoor heat exchanger 23. In addition, the outdoor unit 2 includes a switching mechanism 22 that switches the operating state between a radiation operating state in which the outdoor heat exchanger 23 functions as a radiator of the refrigerant, and an evaporation operating state in which the outdoor heat exchanger 23 functions as an evaporator of the refrigerant. The switching mechanism 22 is connected to the suction side of the compressor 21 via a suction refrigerant pipe 31. The discharge side of the compressor 21 is connected to the switching mechanism 22 via a discharge refrigerant pipe 32. The switching mechanism 22 is connected to the gas side of the outdoor heat exchanger 23 via a first outdoor gas-refrigerant pipe 33. The liquid side of the outdoor heat exchanger 23 is connected to the liquid-refrigerant connection pipe 5 via an outdoor liquid-refrigerant pipe 34. The connection portion of the outdoor liquid-refrigerant pipe 34 with respect to the liquid-refrigerant connection pipe 5 is provided with a liquid-side shutoff valve 27. The switching mechanism 22 is connected to the gas-refrigerant connection pipe 6 via a second outdoor gas-refrigerant pipe 35. The connection portion of the second outdoor gas-refrigerant pipe 35 with respect to the gas-refrigerant connection pipe 6 is provided with a gas-side shutoff valve 28. The liquid-side shutoff valve 27 and the gas-side shutoff valve 28 are valves that are manually opened and closed.

The compressor 21 is a device for compressing the refrigerant. For example, a closed-structure compressor in which a compression element (not illustrated) of positive-displacement type, such as rotary type or scroll type, is rotationally driven by a compressor motor 21 a is used.

The switching mechanism 22 is a device that can switch the flow of the refrigerant in the refrigerant circuit 10 such that, when the outdoor heat exchanger 23 functions as the radiator of the refrigerant (hereinafter, the situation is referred to as “outdoor radiation state”), the switching mechanism 22 connects the discharge side of the compressor 21 to the gas side of the outdoor heat exchanger 23 (see solid lines of the switching mechanism 22 in FIG. 1); and, when the outdoor heat exchanger 23 functions as the evaporator of the refrigerant (hereinafter, the situation is referred to as “outdoor evaporation state”), the switching mechanism 22 connects the suction side of the compressor 21 to the gas side of the outdoor heat exchanger 23 (see broken lines of the switching mechanism 22 in FIG. 1). The switching mechanism 22 is, for example, a four-way switching valve.

The outdoor heat exchanger 23 is a heat exchanger that performs heat exchange between the outdoor air and the refrigerant, which is circulated between the outdoor unit 2 and the indoor units 3 a and 3 b via the liquid-refrigerant connection pipe 5 and the gas-refrigerant connection pipe 6. The outdoor unit 2 includes an outdoor fan 24 that sucks the outdoor air into the outdoor unit 2 that causes the outdoor air to exchange heat with the refrigerant in the outdoor heat exchanger 23, and then that discharges the outdoor air to the outside. That is, the outdoor unit 2 includes the outdoor fan 24 as a fan that sends the outdoor air, which serves as a cooling source or a heating source of the refrigerant flowing through the outdoor heat exchanger 23, to the outdoor heat exchanger 23. The outdoor fan 24 is driven by an outdoor fan motor 24 a.

Focusing only on the compressor 21, the outdoor heat exchanger 23, the liquid-refrigerant connection pipe 5, the indoor expansion valves 51 a and 51 b, the indoor heat exchangers 52 a and 52 b, and the gas-refrigerant connection pipe 6, the air conditioner 1 performs an operation (cooling operation) of circulating the refrigerant in the order of the compressor 21, the outdoor heat exchanger 23, the liquid-refrigerant connection pipe 5, the indoor expansion valves 51 a and 51 b, the indoor heat exchangers 52 a and 52 b, the gas-refrigerant connection pipe 6, and the compressor 21. Focusing only on the compressor 21, the outdoor heat exchanger 23, the liquid-refrigerant connection pipe 5, the indoor expansion valves 51 a and 51 b, the indoor heat exchangers 52 a and 52 b, and the gas-refrigerant connection pipe 6, the air conditioner 1 performs an operation (heating operation) of circulating the refrigerant in the order of the compressor 21, the gas-refrigerant connection pipe 6, the indoor heat exchangers 52 a and 52 b, the indoor expansion valves 51 a and 51 b, the liquid-refrigerant connection pipe 5, the outdoor heat exchanger 23, and the compressor 21. The switching mechanism 22 is switched to the outdoor radiation state in cooling operation, and the switching mechanism 22 is switched to the outdoor evaporation state in heating operation.

In addition, an outdoor expansion valve 25 and a liquid-pressure adjustment expansion valve 26 are provided in the outdoor liquid-refrigerant pipe 34. The outdoor expansion valve 25 is an electric expansion valve that decompresses the refrigerant in heating operation, and is provided in a portion of the outdoor liquid-refrigerant pipe 34 near the liquid side of the outdoor heat exchanger 23. The liquid-pressure adjustment expansion valve 26 is an electric expansion valve that decompresses the refrigerant so that the refrigerant flowing through the liquid-refrigerant connection pipe 5 is brought into a gas-liquid two-phase state in cooling operation, and is provided in a portion of the outdoor liquid-refrigerant pipe 34 near the liquid-refrigerant connection pipe 5. That is, the liquid-pressure adjustment expansion valve 26 is provided in a portion of the outdoor liquid-refrigerant pipe 34 nearer to the liquid-refrigerant connection pipe 5 than the outdoor expansion valve 25.

The air conditioner 1 performs two-phase refrigerant feed of sending the refrigerant in the gas-liquid two-phase state to the liquid-refrigerant connection pipe 5 by the liquid-pressure adjustment expansion valve 26 and hence sending the refrigerant from the outdoor unit 2 to the indoor units 3 a and 3 b in cooling operation.

Furthermore, a refrigerant return pipe 41 is connected to the outdoor liquid-refrigerant pipe 34, and a refrigerant cooler 45 is provided. The refrigerant return pipe 41 is a refrigerant pipe that branches part of the refrigerant flowing through the outdoor liquid-refrigerant pipe 34 and sends the refrigerant to the compressor 21. The refrigerant cooler 45 is a heat exchanger that cools the refrigerant flowing through a portion of the outdoor liquid-refrigerant pipe 34 nearer to the outdoor heat exchanger 23 than the liquid-pressure adjustment expansion valve 26. The outdoor expansion valve 25 is provided in a portion of the outdoor liquid-refrigerant pipe 34 nearer to the outdoor heat exchanger 23 than the refrigerant cooler 45. The liquid-pressure adjustment expansion valve 26 is provided in a portion of the outdoor liquid-refrigerant pipe 34 nearer to the liquid-refrigerant connection pipe 5 than the portion to which the refrigerant cooler 45 is connected (in this case, between the refrigerant cooler 45 and the liquid-side shutoff valve 27).

The refrigerant return pipe 41 is a refrigerant pipe that sends the refrigerant branched from the outdoor liquid-refrigerant pipe 34 to the suction side of the compressor 21. The refrigerant return pipe 41 mainly includes a refrigerant return inlet pipe 42 and a refrigerant return outlet pipe 43. The refrigerant return inlet pipe 42 is a refrigerant pipe that branches part of the refrigerant flowing through the outdoor liquid-refrigerant pipe 34 from a portion between the liquid side of the outdoor heat exchanger 23 and the liquid-pressure adjustment expansion valve 26 (in this case, a portion between the outdoor expansion valve 25 and the refrigerant cooler 45) and sends the refrigerant to the inlet of the refrigerant cooler 45 on the side of the refrigerant return pipe 41. The refrigerant return inlet pipe 42 is provided with a refrigerant return expansion valve 44 that adjusts the flow rate of the refrigerant flowing through the refrigerant cooler 45 while decompressing the refrigerant flowing through the refrigerant return pipe 41. The refrigerant return expansion valve 44 is an electric expansion valve. The refrigerant return outlet pipe 43 is a refrigerant pipe that sends the refrigerant from the outlet of the refrigerant cooler 45 on the side of the refrigerant return pipe 41 to the suction refrigerant pipe 31. The refrigerant cooler 45 cools the refrigerant flowing through the outdoor liquid-refrigerant pipe 34 by using the refrigerant flowing through the refrigerant return pipe 41.

The outdoor unit 2 is provided with various sensors. To be specific, the outdoor unit 2 is provided with a discharge pressure sensor 36 that detects a pressure (discharge pressure Pd) of the refrigerant discharged from the compressor 21. In addition, the outdoor unit 2 is provided with an outdoor heat-exchange liquid-side sensor 37 that detects a temperature Tol (outdoor heat-exchange outlet temperature Tol) of the refrigerant on the liquid side of the outdoor heat exchanger 23, and is provided with a liquid-pipe temperature sensor 38 that detects a temperature (liquid-pipe temperature Tlp) of the refrigerant in a portion of the outdoor liquid-refrigerant pipe 34 between the refrigerant cooler 45 and the liquid-pressure adjustment expansion valve 26.

External Shutoff Valve Unit

The external shutoff valve units 4 a and 4 b are arranged in the building or the like. In this case, the external shutoff valve units 4 a and 4 b are arranged outside the air-conditioning target spaces unlike the indoor units 3 a and 3 b. The external shutoff valve units 4 a and 4 b, together with the gas-refrigerant connection pipe 6, are provided between the indoor units 3 a and 3 b and the outdoor unit 2, and constitute part of the refrigerant circuit 10.

Configurations of the external shutoff valve units 4 a and 4 b are described next. The external shutoff valve unit 4 a and the external shutoff valve unit 4 b have configurations similar to each other. Hence only the configuration of the external shutoff valve unit 4 a is described. For the configuration of the external shutoff valve unit 4 b, the description of the components of the external shutoff valve unit 4 b is omitted while an index “b” is applied to each component instead of the index “a” indicating each component of the external shutoff valve unit 4 a.

The external shutoff valve unit 4 a is provided in the gas-refrigerant connection pipe 6, and mainly includes a gas-side shutoff valve 58 a. In addition, the external shutoff valve unit 4 a includes a gas connection pipe 62 a that is connected to the first branch pipe portion 6 a, which is a portion of the gas-refrigerant connection pipe 6 on the side of the outdoor unit 2, and that is connected to the second branch pipe portion 6 aa, which is a portion of the gas-refrigerant connection pipe 6 on the side of the indoor unit 3 a.

The gas-side shutoff valve 58 a is an electric expansion valve that shuts off the flow of the refrigerant that is circulated between the indoor unit 3 a and the outdoor unit 2 via the gas-refrigerant connection pipe 6. The gas-side shutoff valve 58 a is provided in the gas connection pipe 62 a. That is, the gas-side shutoff valve 58 a is connected to the gas side of the indoor heat exchanger 52 a via the indoor gas-refrigerant pipe 54 a of the indoor unit 3 a, the second branch pipe portion 6 aa of the gas-refrigerant connection pipe 6, and the gas connection pipe 62 a of the external shutoff valve unit 4 a. The gas-side shutoff valve 58 a may not be an electric expansion valve and may be an electromagnetic valve.

The gas connection pipe 62 a mainly includes an indoor-side gas connection pipe 66 a that is connected to a portion of the gas-refrigerant connection pipe 6 on the side of the indoor unit 3 a (in this case, the second branch pipe portion 6 aa), and an outdoor-side gas connection pipe 67 a that is connected to a portion of the gas-refrigerant connection pipe 6 on the side of the outdoor unit 2 (in this case, the first branch pipe portion 6 a). The gas-side shutoff valve 58 a is connected to the indoor-side gas connection pipe 66 a by brazing (the brazing portion is referred to as brazing portion 91 a). The gas-side shutoff valve 58 a is connected to the outdoor-side gas connection pipe 67 a by brazing (the brazing portion is referred to as brazing portion 92 a). The indoor-side gas connection pipe 66 a is connected to the gas-refrigerant connection pipe 6 (in this case, the second branch pipe portion 6 aa) by mechanical pipe joint, such as flare connection (the portion of the mechanical pipe joint is referred to as pipe joint portion 95 a). The pipe joint portion 95 a is connected to the indoor-side gas connection pipe 66 a by brazing (the brazing portion is referred to as brazing portion 95 aa). Although not illustrated here, the indoor-side gas connection pipe 66 a may be directly connected to the gas-refrigerant connection pipe 6 (in this case, the second branch pipe portion 6 aa) by brazing.

The outdoor-side gas connection pipe 67 a is connected to the gas-refrigerant connection pipe 6 (in this case, the first branch pipe portion 6 a) by mechanical pipe joint, such as flare connection (the portion of the mechanical pipe joint is referred to as pipe joint portion 96 a). The pipe joint portion 96 a is connected to the outdoor-side gas connection pipe 67 a by brazing (the brazing portion is referred to as brazing portion 96 aa). Although not illustrated here, the outdoor-side gas connection pipe 67 a may be directly connected to the gas-refrigerant connection pipe 6 (in this case, the first branch pipe portion 6 a) by brazing.

Control Unit

The control unit 19 is constituted by being connected to control boards or the like (not illustrated) provided in, for example, the outdoor unit 2 and the indoor units 3 a and 3 b to communicate therewith. In FIG. 1, however, the control unit 19 is illustrated at a position separated from the outdoor unit 2, the indoor units 3 a and 3 b, and the external shutoff valve units 4 a and 4 b for the convenience of illustration. The control unit 19 controls the components 21, 22, 24, 25, 26, 44, 51 a, 51 b, 55 a, 55 b, 58 a, and 58 b of the air conditioner 1 (in this case, the outdoor unit 2, the indoor units 3 a and 3 b, and the external shutoff valve units 4 a and 4 b), that is, controls the entire operation of the air conditioner 1 in accordance with the detection signals of the above-described various sensors 36, 37, 38, 57 a, and 57 b.

Operation without Leakage of Refrigerant

The operation of the air conditioner 1 when the refrigerant does not leak is described next with reference to FIG. 1. The air conditioner 1 performs cooling operation and heating operation. The air conditioner 1 performs two-phase refrigerant feed of sending the refrigerant in the gas-liquid two-phase state to the liquid-refrigerant connection pipe 5 by the liquid-pressure adjustment expansion valve 26 provided in the outdoor liquid-refrigerant pipe 34 and hence sending the refrigerant from the outdoor unit 2 to the indoor units 3 a and 3 b in cooling operation. The operation of the air conditioner 1 which is described below is performed by the control unit 19 that controls the components of the air conditioner 1.

Cooling Operation

In cooling operation, for example, when all the indoor units 3 a and 3 b perform cooling operation (that is, operation in which all the indoor heat exchangers 52 a and 52 b function as the evaporators of the refrigerant and the outdoor heat exchanger 23 functions as the radiator of the refrigerant), the switching mechanism 22 is switched to the outdoor radiation state (the state in which the switching mechanism 22 is indicated by solid lines in FIG. 1), and the compressor 21, the outdoor fan 24, and the indoor fans 55 a and 55 b are driven.

Then, the high-pressure refrigerant discharged from the compressor 21 is sent to the outdoor heat exchanger 23 via the switching mechanism 22. The refrigerant sent to the outdoor heat exchanger 23 is condensed by being cooled through heat exchange with the outdoor air supplied by the outdoor fan 24 in the outdoor heat exchanger 23 that functions as the radiator of the refrigerant. The refrigerant flows out from the outdoor unit 2 via the outdoor expansion valve 25, the refrigerant cooler 45, the liquid-pressure adjustment expansion valve 26, and the liquid-side shutoff valve 27.

The refrigerant flowing out from the outdoor unit 2 is branched and sent to the indoor units 3 a and 3 b via the liquid-refrigerant connection pipe 5. The refrigerant sent to the indoor units 3 a and 3 b is decompressed by the indoor expansion valves 51 a and 51 b to be at low pressure. The refrigerant is sent to the indoor heat exchangers 52 a and 52 b. The refrigerant sent to the indoor heat exchangers 52 a and 52 b is evaporated by being heated through heat exchange with the indoor air supplied from the air-conditioning target spaces by the indoor fans 55 a and 55 b in the indoor heat exchangers 52 a and 52 b that function as the evaporators of the refrigerant. The refrigerant flows out from the indoor units 3 a and 3 b. The indoor air cooled by the indoor heat exchangers 52 a and 52 b is sent to the air-conditioning target spaces and the air-conditioning target spaces are cooled by using the cooled indoor air.

The refrigerant flowing out from the indoor units 3 a and 3 b is sent to the external shutoff valve units 4 a and 4 b via the second branch pipe portions 6 aa and 6 bb of the gas-refrigerant connection pipe 6. The refrigerant sent to the external shutoff valve units 4 a and 4 b passes through the gas-side shutoff valves 58 a and 58 b and then flows out from the external shutoff valve units 4 a and 4 b.

The refrigerant flowing out from the external shutoff valve units 4 a and 4 b is joined at the gas-refrigerant connection pipe 6 and sent to the outdoor unit 2. The refrigerant sent to the outdoor unit 2 is sucked into the compressor 21 via the gas-side shutoff valve 28 and the switching mechanism 22.

In the above-described cooling operation, the air conditioner 1 performs two-phase refrigerant feed of sending the refrigerant in the gas-liquid two-phase state to the liquid-refrigerant connection pipe 5 by the liquid-pressure adjustment expansion valve 26 and hence sending the refrigerant from the outdoor unit 2 to the indoor units 3 a and 3 b. In addition, the refrigerant flowing through the outdoor liquid-refrigerant pipe 34 is cooled by the refrigerant return pipe 41 and the refrigerant cooler 45 to reduce variation in the liquid-pipe temperature Tlp in the portion of the outdoor liquid-refrigerant pipe 34 between the refrigerant cooler 45 and the liquid-pressure adjustment expansion valve 26, so that the two-phase refrigerant feed can be properly performed.

First, the control unit 19 causes the liquid-pressure adjustment expansion valve 26 to decompress the refrigerant so that the refrigerant flowing through the liquid-refrigerant connection pipe 5 is brought into the gas-liquid two-phase state. The refrigerant decompressed by the liquid-pressure adjustment expansion valve 26 is the refrigerant at medium pressure that is lower than the pressure of the high-pressure refrigerant and higher than the pressure of the low-pressure refrigerant. The control unit 19 controls the opening degree of the liquid-pressure adjustment expansion valve 26 so that a degree of subcooling SCo of the refrigerant on the liquid side of the outdoor heat exchanger 23 becomes a target degree of subcooling SCot. To be specific, the control unit 19 obtains the degree of subcooling SCo of the refrigerant on the liquid side of the outdoor heat exchanger 23 from the outdoor heat-exchange liquid-side temperature Tol. The control unit 19 obtains the degree of subcooling SCo of the refrigerant on the liquid side of the outdoor heat exchanger 23 by subtracting the outdoor heat-exchange outlet temperature Tol from a temperature Toc of the refrigerant, which is obtained by converting the discharge pressure Pd into a saturation temperature. The control unit 19 performs control to increase the opening degree of the liquid-pressure adjustment expansion valve 26 if the degree of subcooling SCo is larger than the target degree of subcooling SCot, and performs control to decrease the opening degree of the liquid-pressure adjustment expansion valve 26 if the degree of subcooling SCo is smaller than the target degree of subcooling SCot. At this time, the control unit 19 performs control to fix the opening degree of the outdoor expansion valve 25 to a fully opened state.

With this control, the refrigerant flowing through the liquid-refrigerant connection pipe 5 is brought into the gas-liquid two-phase state. Hence, the liquid-refrigerant connection pipe 5 is less likely filled with the refrigerant in the liquid state as compared with the case where the refrigerant flowing through the liquid-refrigerant connection pipe 5 is in the liquid state. The amount of refrigerant existing in the liquid-refrigerant connection pipe 5 can be decreased by that amount.

The control unit 19 causes the temperature (the liquid-pipe temperature Tlp) of the refrigerant in the portion of the outdoor liquid-refrigerant pipe 34 between the refrigerant cooler 45 and the liquid-pressure adjustment expansion valve 26 to be constant by cooling the refrigerant flowing through the portion of the outdoor liquid-refrigerant pipe 34 nearer to the outdoor heat exchanger 23 than the liquid-pressure adjustment expansion valve 26 by the refrigerant cooler 45 by using the refrigerant flowing through the refrigerant return pipe 41. The control unit 19 controls the opening degree of the refrigerant return expansion valve 44 so that the temperature (the liquid-pipe temperature Tlp) of the refrigerant in the portion of the outdoor liquid-refrigerant pipe 34 between the refrigerant cooler 45 and the liquid-pressure adjustment expansion valve 26 becomes a target liquid-pipe temperature Tlpt. To be specific, the control unit 19 performs control to increase the opening degree of the refrigerant return expansion valve 44 if the liquid-pipe temperature Tlp is higher than the target liquid-pipe temperature Tlpt, and performs control to decrease the opening degree of the refrigerant return expansion valve 44 if the liquid-pipe temperature Tlp is lower than the target liquid-pipe temperature Tlpt.

With the control, the temperature (the liquid-pipe temperature Tlp) of the refrigerant in the portion of the outdoor liquid-refrigerant pipe 34 between the refrigerant cooler 45 and the liquid-pressure adjustment expansion valve 26 can be maintained constant at the target liquid-pipe temperature Tlpt. By making the liquid-pipe temperature Tlp constant and reducing variation, the refrigerant flowing through the liquid-refrigerant connection pipe 5 after decompressed by the liquid-pressure adjustment expansion valve 26 can be reliably maintained in a desirable gas-liquid two-phase state.

Heating Operation

In heating operation, for example, when all the indoor units 3 a and 3 b perform heating operation (that is, operation in which all the indoor heat exchangers 52 a and 52 b function as the radiators of the refrigerant and the outdoor heat exchanger 23 functions as the evaporator of the refrigerant), the switching mechanism 22 is switched to the outdoor evaporation state (the state in which the switching mechanism 22 is indicated by broken lines in FIG. 1), and the compressor 21, the outdoor fan 24, and the indoor fans 55 a and 55 b are driven.

Then, the high-pressure refrigerant discharged from the compressor 21 flows out from the outdoor unit 2 via the switching mechanism 22 and the gas-side shutoff valve 28.

The refrigerant flowing out from the outdoor unit 2 is branched and sent to the external shutoff valve units 4 a and 4 b via the gas-refrigerant connection pipe 6. The refrigerant sent to the external shutoff valve units 4 a and 4 b passes through the gas-side shutoff valves 58 a and 58 b and then flows out from the external shutoff valve units 4 a and 4 b.

The refrigerant flowing out from the external shutoff valve units 4 a and 4 b is sent to the indoor units 3 a and 3 b via the second branch pipe portions 6 aa and 6 bb of the gas-refrigerant connection pipe 6. The refrigerant sent to the indoor units 3 a and 3 b is sent to the indoor heat exchangers 52 a and 52 b. The high-pressure refrigerant sent to the indoor heat exchangers 52 a and 52 b is condensed by being cooled through heat exchange with the indoor air supplied from the air-conditioning target spaces by the indoor fans 55 a and 55 b in the indoor heat exchangers 52 a and 52 b that function as the radiators of the refrigerant. The refrigerant flows out from the indoor units 3 a and 3 b via the indoor expansion valves 51 a and 51 b. The indoor air heated by the indoor heat exchangers 52 a and 52 b is sent to the air-conditioning target spaces and the air-conditioning target spaces are heated by using the heated indoor air.

The refrigerant flowing out from the indoor units 3 a and 3 b is joined at the liquid-refrigerant connection pipe 5 and sent to the outdoor unit 2. The refrigerant sent to the outdoor unit 2 is sent to the outdoor expansion valve 25 via the liquid-side shutoff valve 27, the liquid-pressure adjustment expansion valve 26, and the refrigerant cooler 45. The refrigerant sent to the outdoor expansion valve 25 is decompressed by the outdoor expansion valve 25 to be at low pressure and then is sent to the outdoor heat exchanger 23. The refrigerant sent to the outdoor heat exchanger 23 is evaporated by being heated through heat exchange with the outdoor air supplied by the outdoor fan 24. The refrigerant is sucked into the compressor 21 via the switching mechanism 22.

In the above-described heating operation, unlike cooling operation, the control unit 19 performs control to fix the opening degree of the liquid-pressure adjustment expansion valve 26 to a fully opened state. The opening degree of the refrigerant return expansion valve 44 is brought into a fully closed state to inhibit the refrigerant from flowing to the refrigerant return pipe 41.

Operation with Leakage of Refrigerant

The operation of the air conditioner 1 when the refrigerant leaks is described next with reference to FIGS. 1 to 3. FIG. 3 is a flowchart of an operation when a refrigerant leaks in the air conditioner 1 according to one or more embodiments of the present invention. The operation of the air conditioner 1 when the refrigerant leaks which is described below is performed by the control unit 19 that controls the components of the air conditioner 1 (the outdoor unit 2, the indoor units 3 a and 3 b, and the external shutoff valve units 4 a and 4 b) like the operation when the refrigerant does not leak.

The air conditioner 1 is provided with the refrigerant sensors 57 a and 57 b serving as the refrigerant leakage detecting means as described above. When the refrigerant sensors 57 a and 57 b detect leakage of the refrigerant, the indoor expansion valves 51 a and 51 b and the gas-side shutoff valves 58 a and 58 b are closed in accordance with the information of the refrigerant sensors 57 a and 57 b. Thus, the indoor units 3 a and 3 b can be isolated. Accordingly, the refrigerant can be inhibited from flowing from the refrigerant connection pipes 5 and 6 to the indoor units 3 a and 3 b. That is, when the refrigerant leaks, the indoor expansion valves 51 a and 51 b are used also as liquid-side shutoff valves and are closed together with the gas-side shutoff valves 58 a and 58 b, thereby providing a refrigerant shutoff function when the refrigerant leaks from the indoor units 3 a and 3 b.

To be specific, when the refrigerant sensors 57 a and 57 b detect leakage of the refrigerant (step ST1), the control unit 19 closes the indoor expansion valves 51 a and 51 b and the gas-side shutoff valves 58 a and 58 b (step ST4). In addition, when leakage of the refrigerant is detected in step ST1, an alarm may be given (step ST2). Further, before the indoor expansion valves 51 a and 51 b and the gas-side shutoff valves 58 a and 58 b are closed, the compressor 21 may be stopped (step ST3) to suppress an excessive increase in the pressure of the refrigerant.

In this way, the indoor expansion valves 51 a and 51 b and the gas-side shutoff valves 58 a and 58 b are closed in accordance with the information of the refrigerant sensors 57 a and 57 b serving as the refrigerant leakage detecting means when the refrigerant leaks. Thus, the refrigerant is inhibited from flowing from the refrigerant connection pipes 5 and 6 to the indoor units 3 a and 3 b, and increase in concentration of the refrigerant in the air-conditioning target spaces can be suppressed.

Features

The air conditioner 1 and the indoor units 3 a and 3 b according to one or more embodiments have the following features.

To add the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor units 3 a and 3 b, providing shutoff valves on both the liquid sides and the gas sides of the indoor units 3 a and 3 b may increase the cost and the sizes of the indoor units 3 a and 3 b. To reduce the increase in the cost and the sizes of the indoor units 3 a and 3 b as much as possible, it is desirable to use the indoor expansion valves 51 a and 51 b also as liquid-side shutoff valves for the situation in which the refrigerant leaks from the indoor units 3 a and 3 b.

In the indoor units 3 a and 3 b arranged in the air-conditioning target spaces, however, the connection-side indoor liquid-refrigerant pipes 72 a and 72 b that connect the indoor expansion valves 51 a and 51 b to the liquid-refrigerant connection pipe 5 are connected to the indoor expansion valves 51 a and 51 b by brazing. The brazing portions 82 a and 82 b brazing the indoor expansion valves 51 a and 51 b and the connection-side indoor liquid-refrigerant pipes 72 a and 72 b may corrode and the refrigerant may leak from the corroding portions. When the refrigerant leaks from the brazing portions 82 a and 82 b, the refrigerant is continuously supplied from the liquid-refrigerant connection pipe 5 to the brazing portions 82 a and 82 b although the indoor expansion valves 51 a and 51 b are closed to function as the shutoff valves on the liquid sides of the indoor units 3 a and 3 b. The refrigerant may continuously leak from the indoor units 3 a and 3 b to the air-conditioning target spaces. Thus, it is difficult to use the indoor expansion valves 51 a and 51 b also as the shutoff valves on the liquid sides of the indoor units 3 a and 3 b unless such leakage of the refrigerant from the brazing portions 82 a and 82 b is reduced.

In this case, by providing the coating materials 11 a and 11 b at the brazing portions 82 a and 82 b as described above, leakage of the refrigerant from the brazing portions 82 a and 82 b is reduced, and the indoor expansion valves 51 a and 51 b can be used also as the shutoff valves on the liquid sides of the indoor units 3 a and 3 b. As long as the indoor expansion valves 51 a and 51 b can be used also as the shutoff valves on the liquid sides of the indoor units 3 a and 3 b, the increase in the cost and the sizes of the indoor units 3 a and 3 b can be suppressed by that amount.

Accordingly, the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor units 3 a and 3 b can be added while the increase in the cost and the sizes of the indoor units 3 a and 3 b due to the provision of the shutoff valves on the liquid sides of the indoor units 3 a and 3 b is reduced as much as possible.

In particular, since the gas-side shutoff valves 58 a and 58 b are arranged in the external shutoff valve units 4 a and 4 b located outside the indoor units 3 a and 3 b as described above, the increase in the sizes of the indoor units 3 a and 3 b can be suppressed.

Since the outdoor unit 2 includes the liquid-pressure adjustment expansion valve 26 as described above, the two-phase refrigerant feed of decompressing the refrigerant to be brought into the gas-liquid two-phase state in the outdoor unit 2 and then sending the refrigerant to the indoor units 3 a and 3 b via the liquid-refrigerant connection pipe 5 can be performed. Thus, the amount of refrigerant held by the entire air conditioner can be decreased by the amount by which the refrigerant flowing through the liquid-refrigerant connection pipe 5 turns into the gas-liquid two-phase state through the two-phase refrigerant feed. However, although the amount of refrigerant held by the entire air conditioner can be decreased by a certain degree through the two-phase refrigerant feed, when the refrigerant leaks from the indoor units 3 a and 3 b, the concentration of the refrigerant increases in the air-conditioning target spaces where the indoor units 3 a and 3 b involving leakage of the refrigerant are arranged, and the concentration may exceed its permissible value. In such a case, the two-phase refrigerant feed is not occasionally sufficient for the countermeasure to leakage of the refrigerant.

In this case, by providing the coating materials 11 a and 11 b at the brazing portions 82 a and 82 b as described above, leakage of the refrigerant from the brazing portions 82 a and 82 b is reduced, and the indoor expansion valves 51 a and 51 b can be used also as the shutoff valves on the liquid sides of the indoor units 3 a and 3 b.

Accordingly, even in the case where the two-phase refrigerant feed is not sufficient for the countermeasure to leakage of the refrigerant, the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor units 3 a and 3 b can be added while the increase in the cost and the sizes of the indoor units 3 a and 3 b due to the provision of the shutoff valves on the liquid sides of the indoor units 3 a and 3 b is reduced as much as possible. The addition of the refrigerant shutoff function makes the countermeasure to leakage of the refrigerant sufficient.

First Modification

In one or more embodiments, only the indoor expansion valves 51 a and 51 b are provided in the indoor liquid-refrigerant pipes 53 a and 53 b as illustrated in FIG. 2 in the indoor units 3 a and 3 b arranged in the air-conditioning target spaces. In addition, filters 73 a and 73 b for reducing inflow of foreign substances and so forth to the indoor expansion valves 51 a and 51 b may be provided in the connection-side indoor liquid-refrigerant pipes 72 a and 72 b as illustrated in FIG. 4 in the indoor units 3 a and 3 b. The filters 73 a and 73 b are also connected to the connection-side indoor liquid-refrigerant pipes 72 a and 72 b by brazing. The connection-side indoor liquid-refrigerant pipes 72 a and 72 b include first connection-side indoor liquid-refrigerant pipes 74 a and 74 b connected to the indoor expansion valves 51 a and 51 b, and second connection-side indoor liquid-refrigerant pipes 75 a and 75 b connected to the liquid-refrigerant connection pipe 5 (in this case, the branch pipe portions 5 a and 5 b). The filters 73 a and 73 b are connected between the first connection-side indoor liquid-refrigerant pipes 74 a and 74 b and the second connection-side indoor liquid-refrigerant pipes 75 a and 75 b. The filters 73 a and 73 b are connected to the first connection-side indoor liquid-refrigerant pipes 74 a and 74 b and the second connection-side indoor liquid-refrigerant pipes 75 a and 75 b by brazing (the brazing portions are referred to as brazing portions 85 a, 85 b, 86 a, and 86 b). Due to this, the brazing portions 85 a, 85 b, 86 a, and 86 b may corrode and the refrigerant may leak from the corroding portions. This makes difficult to use the indoor expansion valves 51 a and 51 b also as the shutoff valves on the liquid sides of the indoor units 3 a and 3 b, like the brazing portions 82 a and 82 b brazing the indoor expansion valves 51 a and 51 b and the connection-side indoor liquid-refrigerant pipes 72 a and 72 b (the first connection-side indoor liquid-refrigerant pipes 74 a and 74 b).

To address this, as illustrated in FIG. 4, the brazing portions 85 a, 85 b, 86 a, and 86 b brazing the filters 73 a and 73 b with the first connection-side indoor liquid-refrigerant pipes 74 a and 74 b and the second connection-side indoor liquid-refrigerant pipes 75 a and 75 b are also provided with coating materials 11 a, 11 b, 12 a, and 12 b. The first connection-side indoor liquid-refrigerant pipes 74 a and 74 b including the brazing portions 82 a and 82 b and the brazing portions 85 a and 85 b are provided with the coating materials 11 a and 11 b. The second connection-side indoor liquid-refrigerant pipes 75 a and 75 b including the brazing portions 86 a and 86 b and the brazing portions 83 aa and 83 bb are provided with the coating materials 12 a and 12 b. When the second connection-side indoor liquid-refrigerant pipes 75 a and 75 b are directly connected to the liquid-refrigerant connection pipe 5 (in this case, the branch pipe portion 5 a) by brazing, the coating materials 12 a and 12 b may be provided to include the brazing portions brazing the second connection-side indoor liquid-refrigerant pipes 75 a and 75 b and the liquid-refrigerant connection pipe 5 (in this case, the branch pipe portion 5 a). The way of providing the coating materials is not limited to the above. A coating material may be provided at each of the brazing portions 82 a, 82 b, 85 a, 85 b, 86 a, 86 b, 83 aa, and 83 bb, or may be provided collectively at all the brazing portions 82 a, 82 b, 85 a, 85 b, 86 a, 86 b, 83 aa, and 83 bb including the filters 73 a and 73 b. Accordingly, leakage of the refrigerant from the brazing portions 85 a, 85 b, 86 a, and 86 b brazing the filters 73 a and 73 b with the first connection-side indoor liquid-refrigerant pipes 74 a and 74 b and the second connection-side indoor liquid-refrigerant pipes 75 a and 75 b is suppressed, so that the indoor expansion valves 51 a and 51 b can be used also as the shutoff valves on the liquid sides of the indoor units 3 a and 3 b.

Even in the case where the filters 73 a and 73 b are provided in the connection-side indoor liquid-refrigerant pipes 72 a and 72 b, the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor units 3 a and 3 b can be added while the increase in the cost and the sizes of the indoor units 3 a and 3 b due to the provision of the shutoff valves on the liquid sides of the indoor units 3 a and 3 b is reduced as much as possible.

Second Modification

In the external shutoff valve units 4 a and 4 b, the gas-side shutoff valves 58 a and 58 b are connected to the gas connection pipes 62 a and 62 b connected to the gas-refrigerant connection pipe 6 (the indoor-side gas connection pipes 66 a and 66 b and the outdoor-side gas connection pipes 67 a and 67 b) by brazing. Due to this, the brazing portions 92 a and 92 b brazing the gas-side shutoff valves 58 a and 58 b and the outdoor-side gas connection pipes 67 a and 67 b may corrode and the refrigerant may leak from the corroding portions. In one or more embodiments, however, the external shutoff valve units 4 a and 4 b are arranged outside the air-conditioning target spaces. Hence, even when the refrigerant leaks from the brazing portions 92 a and 92 b, the refrigerant hardly leaks to the air-conditioning target spaces. In contrast, when the external shutoff valve units 4 a and 4 b are arranged in the air-conditioning target spaces together with the indoor units 3 a and 3 b, if the refrigerant leaks from the brazing portions 92 a and 92 b, the refrigerant is continuously supplied from the gas-refrigerant connection pipe 6 to the brazing portions 92 a and 92 b although the gas-side shutoff valves 58 a and 58 b are closed, and the refrigerant may continuously leak from the external shutoff valve units 4 a and 4 b to the air-conditioning target spaces. Thus, it is required to reduce leakage of the refrigerant from the brazing portions 92 a and 92 b.

To address this, as illustrated in FIG. 5, the brazing portions 92 a and 92 b brazing the gas-side shutoff valves 58 a and 58 b and the outdoor-side gas connection pipes 67 a and 67 b are also provided with coating materials 13 a and 13 b. The coating materials 13 a and 13 b may be provided at only the brazing portions 92 a and 92 b, or may be also provided at a portion other than the brazing portions 92 a and 92 b. For example, as illustrated in FIG. 5, the coating materials 13 a and 13 b may be provided in a range from the gas-side shutoff valves 58 a and 58 b to the pipe joint portions 96 a and 96 b of the outdoor-side gas connection pipes 67 a and 67 b (that is, so as to include the brazing portions 92 a and 92 b and the brazing portions 96 aa and 96 bb). When the outdoor-side gas connection pipes 67 a and 67 b are directly connected to the gas-refrigerant connection pipe 6 (in this case, the first branch pipe portions 6 a and 6 b) by brazing, the coating materials 13 a and 13 b may be provided in a range from the gas-side shutoff valves 58 a and 58 b to the brazing portions brazing the outdoor-side gas connection pipes 67 a and 67 b and the gas-refrigerant connection pipe 6 (in this case, the first branch pipe portions 6 a and 6 b). Accordingly, leakage of the refrigerant from the brazing portions 92 a and 92 b brazing the gas-side shutoff valves 58 a and 58 b and the outdoor-side gas connection pipes 67 a and 67 b is reduced, and the external shutoff valve units 4 a and 4 b can be arranged in the air-conditioning target spaces together with the indoor units 3 a and 3 b. Referring to FIG. 5, in the configuration of one or more embodiments (see FIG. 2) without the filters 73 a and 73 b, the brazing portions 92 a and 92 b brazing the gas-side shutoff valves 58 a and 58 b and the outdoor-side gas connection pipes 67 a and 67 b are provided with the coating materials 13 a and 13 b; however, it is not limited to the above. For example, in the configuration of the above-described first modification (see FIG. 4) with the filters 73 a and 73 b, the brazing portions 92 a and 92 b brazing the gas-side shutoff valves 58 a and 58 b and the outdoor-side gas connection pipes 67 a and 67 b may be provided with the coating materials 13 a and 13 b.

Accordingly, the degree of freedom is ensured for arrangement of the external shutoff valve units 4 a and 4 b.

Third Modification

In one or more embodiments, to add the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor units 3 a and 3 b, the indoor expansion valves 51 a and 51 b of the indoor units 3 a and 3 b are used also as the liquid-side shutoff valves. In addition, the gas-side shutoff valves 58 a and 58 b are provided at the external shutoff valve units 4 a and 4 b. However, to add the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor units, the gas-side shutoff valves 58 a and 58 b may be provided at the indoor units 3 a and 3 b as illustrated in FIG. 6 instead of providing the gas-side shutoff valves 58 a and 58 b in the external shutoff valve units 4 a and 4 b. The indoor gas-refrigerant pipes 54 a and 54 b mainly include heat-exchange-side indoor gas-refrigerant pipes 76 a and 76 b that connect the gas sides of the indoor heat exchangers 52 a and 52 b to the gas-side shutoff valves 58 a and 58 b, and connection-side indoor gas-refrigerant pipes 77 a and 77 b that connect the gas-side shutoff valves 58 a and 58 b to the gas-refrigerant connection pipe 6 (in this case, the branch pipe portions 6 a and 6 b). In this case, the heat-exchange-side indoor gas-refrigerant pipes 76 a and 76 b are connected to the gas-side shutoff valves 58 a and 58 b by brazing (the brazing portions are referred to as brazing portions 87 a and 87 b), and the gas-side shutoff valves 58 a and 58 b are connected to the connection-side indoor gas-refrigerant pipes 77 a and 77 b by brazing (the brazing portions are referred to as brazing portions 88 a and 88 b). Due to this, the brazing portions 88 a and 88 b brazing the gas-side shutoff valves 58 a and 58 b and the connection-side indoor gas-refrigerant pipes 77 a and 77 b may corrode and the refrigerant may leak from the corroding portions. When the refrigerant leaks from the brazing portions 88 a and 88 b, the refrigerant is continuously supplied from the gas-refrigerant connection pipe 6 to the brazing portions 88 a and 88 b although the gas-side shutoff valves 58 a and 58 b are closed. The refrigerant may continuously leak from the indoor units 3 a and 3 b to the air-conditioning target spaces. Thus, it is required to reduce leakage of the refrigerant from the brazing portions 88 a and 88 b.

To address this, as illustrated in FIG. 7, the brazing portions 88 a and 88 b brazing the gas-side shutoff valves 58 a and 58 b and the connection-side indoor gas-refrigerant pipes 77 a and 77 b are provided with coating materials 15 a and 15 b. The coating materials 15 a and 15 b may be provided at only the brazing portions 88 a and 88 b, or may be also provided at a portion other than the brazing portions 88 a and 88 b. For example, as illustrated in FIG. 7, the coating materials 15 a and 15 b may be provided in a range from the gas-side shutoff valves 58 a and 58 b to the pipe joint portions 84 a and 84 b of the connection-side indoor gas-refrigerant pipes 77 a and 77 b (that is, so as to include the brazing portions 88 a and 88 b and the brazing portions 84 aa and 84 bb). When the connection-side indoor gas-refrigerant pipes 77 a and 77 b are directly connected to the gas-refrigerant connection pipe 6 (in this case, the branch pipe portions 6 a and 6 b) by brazing, the coating materials 15 a and 15 b may be provided in a range from the gas-side shutoff valves 58 a and 58 b to the brazing portions brazing the connection-side indoor gas-refrigerant pipes 77 a and 77 b and the gas-refrigerant connection pipe 6 (in this case, the branch pipe portions 6 a and 6 b). Accordingly, leakage of the refrigerant from the brazing portions 88 a and 88 b brazing the gas-side shutoff valves 58 a and 58 b and the connection-side indoor gas-refrigerant pipes 77 a and 77 b is reduced. Referring to FIG. 7, in the configuration of one or more embodiments (see FIG. 2) without the filters 73 a and 73 b, the gas-side shutoff valves 58 a and 58 b are provided in the indoor units 3 a and 3 b, and the brazing portions 88 a and 88 b brazing the gas-side shutoff valves 58 a and 58 b and the connection-side indoor gas-refrigerant pipes 77 a and 77 b are provided with the coating materials 15 a and 15 b; however, it is not limited to the above. For example, in the configuration of the above-described first modification (see FIG. 4) with the filters 73 a and 73 b, the gas-side shutoff valves 58 a and 58 b may be provided at the indoor unit 3 a and 3 b, and the brazing portions 88 a and 88 b brazing the gas-side shutoff valves 58 a and 58 b and the connection-side indoor gas-refrigerant pipes 77 a and 77 b may be provided with the coating materials 15 a and 15 b.

Accordingly, the shutoff valves provided at the indoor units 3 a and 3 b are provided on only the gas side, and the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor units 3 a and 3 b can be added.

Fourth Modification

In one or more embodiments, as illustrated in FIG. 3, when the refrigerant sensors 57 a and 57 b detect leakage of the refrigerant, all the indoor expansion valves 51 a and 51 b and the gas-side shutoff valves 58 a and 58 b are closed and the compressor 21 is stopped in accordance with the information of the refrigerant sensors 57 a and 57 b. Accordingly, the circulation of the refrigerant in the refrigerant circuit 10 is stopped, and the cooling operation or heating operation is stopped not only in the indoor unit in which the refrigerant leaks but also in the indoor unit in which the refrigerant does not leak.

It is desirable that only the indoor unit in which the refrigerant leaks is isolated whereas the indoor unit in which the refrigerant does not leak can continue cooling operation or heating operation.

As illustrated in FIG. 8, when the refrigerant sensors 57 a and 57 b detect leakage of the refrigerant (step ST1), the control unit 19 closes only the indoor expansion valve and the gas-side shutoff valve corresponding to the indoor unit in which the refrigerant leaks among a plurality of indoor units 3 a and 3 b (step ST5). Then, by continuing the circulation of the refrigerant in the refrigerant circuit 10 without stopping the compressor 21, the cooling operation or heating operation of the indoor unit in which the refrigerant does not leak is continued (step ST6).

When the refrigerant leaks from the indoor units 3 a and 3 b, only the indoor unit in which the refrigerant leaks is isolated whereas the indoor unit in which the refrigerant does not leak can continue the operation.

Fifth Modification

In one or more embodiments, when the gas-side shutoff valves 58 a and 58 b are provided, the external shutoff valve units 4 a and 4 b corresponding to the indoor units 3 a and 3 b are provided. However, it is not limited thereto. For example, an external shutoff valve unit in which the external shutoff valve units 4 a and 4 b may be integrated, that is, an external shutoff valve unit including both the gas-side shutoff valves 58 a and 58 b may be employed.

Configuration

FIG. 9 is a schematic configuration diagram of an air conditioner 1 according to one or more embodiments of the present invention. FIG. 10 illustrates a refrigerant system in the periphery of indoor units 3 a, 3 b, 3 c, and 3 d and relay units 4 a, 4 b, 4 c, and 4 d constituting the air conditioner 1 according to one or more embodiments of the present invention.

The air conditioner 1 is an apparatus that performs air conditioning (cooling and heating) in an air-conditioning target space in a building or the like through a vapor compression refrigeration cycle. The air conditioner 1 mainly includes an outdoor unit 2; a plurality of (in this case, four) indoor units 3 a, 3 b, 3 c, and 3 d mutually connected in parallel; relay units 4 a, 4 b, 4 c, and 4 d respectively connected to the indoor units 3 a, 3 b, 3 c, and 3 d; a liquid-refrigerant connection pipe 5 and a gas-refrigerant connection pipe 6 that connect the outdoor unit 2 to the indoor units 3 a, 3 b, 3 c, and 3 d via the relay units 4 a, 4 b, 4 c, and 4 d; and a control unit 19 that controls components of the outdoor unit 2, the indoor units 3 a, 3 b, 3 c, and 3 d, and the relay units 4 a, 4 b, 4 c, and 4 d. A vapor compression refrigerant circuit 10 of the air conditioner 1 is constituted by connecting the outdoor unit 2, the plurality of indoor units 3 a, 3 b, 3 c, and 3 d, the plurality of relay units 4 a, 4 b, 4 c, and 4 d, the liquid-refrigerant connection pipe 5, and the gas-refrigerant connection pipe 6. The refrigerant circuit 10 is filled with a refrigerant such as R32. In the air conditioner 1, the indoor units 3 a, 3 b, 3 c, and 3 d can individually perform cooling operation or heating operation by using the relay units 4 a, 4 b, 4 c, and 4 d. By sending the refrigerant from the indoor unit that performs heating operation to the indoor unit that performs cooling operation, heat is recovered between the indoor units (in this case, cooling and heating mixed operation in which cooling operation and heating operation can be simultaneously performed).

Connection Pipe

The liquid-refrigerant connection pipe 5 mainly includes a joint pipe portion extending from the outdoor unit 2, first branch pipe portions 5 a, 5 b, 5 c, and 5 d branched at a position before the relay units 4 a, 4 b, 4 c, and 4 d into a plurality of (in this case, four) pipe portions, and second branch pipe portions 5 aa, 5 bb, 5 cc, and 5 dd that connect the relay units 4 a, 4 b, 4 c, and 4 d to the indoor units 3 a, 3 b, 3 c, and 3 d.

The gas-refrigerant connection pipe 6 mainly includes a high/low-pressure gas-refrigerant connection pipe 7, a low-pressure gas-refrigerant connection pipe 8, and branch pipe portions 6 a, 6 b, 6 c, and 6 d that connect the relay units 4 a, 4 b, 4 c, and 4 d to the indoor units 3 a, 3 b, 3 c, and 3 d. The high/low-pressure gas-refrigerant connection pipe 7 is a gas-refrigerant connection pipe that can switch connection to the discharge side or the suction side of a compressor 21 (described later), and includes a joint pipe portion extending from the outdoor unit 2, and a plurality of (in this case, four) branch pipe portions 7 a, 7 b, 7 c, and 7 d branched at a position before the relay units 4 a, 4 b, 4 c, and 4 d. The low-pressure gas-refrigerant connection pipe 8 is a gas-refrigerant connection pipe connected to the suction side of the compressor 21 (described later), and includes a joint pipe portion extending from the outdoor unit 2, and branch pipe portions 8 a, 8 b, 8 c, and 8 d branched at a position before the relay units 4 a, 4 b, 4 c, and 4 d into a plurality of (in this case, four) pipe portions. In this way, since the gas-refrigerant connection pipe 6 includes the high/low-pressure gas-refrigerant connection pipe 7 and the low-pressure gas-refrigerant connection pipe 8, the configuration includes three connection pipes including the liquid-refrigerant connection pipe 5 (that is, three-pipe configuration).

Indoor Unit

The indoor units 3 a, 3 b, 3 c, and 3 d are arranged in air-conditioning target spaces in a building or the like. Being “arranged in air-conditioning target spaces” includes a situation in which the indoor units 3 a, 3 b, 3 c, and 3 d are installed in the air-conditioning target spaces and a situation in which the indoor units 3 a, 3 b, 3 c, and 3 d are not arranged in the air-conditioning target spaces but the indoor units 3 a, 3 b, 3 c, and 3 d are connected to the air-conditioning target spaces via air ducts or the like. The indoor units 3 a, 3 b, 3 c, and 3 d are connected to the outdoor unit 2 via the liquid-refrigerant connection pipe 5, the gas-refrigerant connection pipe 6 (the high/low-pressure gas-refrigerant connection pipe 7, the low-pressure gas-refrigerant connection pipe 8, and the branch pipe portions 6 a, 6 b, 6 c, and 6 d), and the relay units 4 a, 4 b, 4 c, and 4 d, and constitute part of the refrigerant circuit 10 as described above.

Configurations of the indoor units 3 a, 3 b, 3 c, and 3 d are described next. The indoor unit 3 a and the indoor units 3 b, 3 c, and 3 d have configurations similar to one another. Hence only the configuration of the indoor unit 3 a is described. For the configurations of the indoor units 3 b, 3 c, and 3 d, the description of the components of the indoor units 3 b, 3 c, and 3 d is omitted while an index “b”, “c”, or “d” is applied to each component instead of the index “a” indicating each component of the indoor unit 3 a.

The indoor unit 3 a mainly includes an indoor expansion valve 51 a and an indoor heat exchanger 52 a. In addition, the indoor unit 3 a includes an indoor liquid-refrigerant pipe 53 a that connects the liquid side of the indoor heat exchanger 52 a to the liquid-refrigerant connection pipe 5 (in this case, the branch pipe portion 5 a), and an indoor gas-refrigerant pipe 54 a that connects the gas side of the indoor heat exchanger 52 a to the gas-refrigerant connection pipe 6 (in this case, the second branch pipe portion 6 aa). The indoor expansion valve 51 a, the indoor heat exchanger 52 a, the indoor liquid-refrigerant pipe 53 a, and the indoor gas-refrigerant pipe 54 a are similar to the indoor expansion valve 51 a, the indoor heat exchanger 52 a, the indoor liquid-refrigerant pipe 53 a, and the indoor gas-refrigerant pipe 54 a of the indoor unit 3 a according to one or more embodiments. Thus, the description thereof is omitted.

A brazing portion 82 a brazing the indoor expansion valve 51 a and a connection-side indoor liquid-refrigerant pipe 72 a is provided with a coating material 11 a, like the indoor unit 3 a according to one or more embodiments.

The indoor unit 3 a is provided with a refrigerant sensor 57 a serving as refrigerant leakage detecting means for detecting leakage of the refrigerant, like the indoor unit 3 a according to one or more embodiments.

Outdoor Unit

The outdoor unit 2 is arranged outside the air-conditioning target spaces or outside the building or the like. The outdoor unit 2 is connected to the indoor units 3 a, 3 b, 3 c, and 3 d via the liquid-refrigerant connection pipe 5, the gas-refrigerant connection pipe 6 (the high/low-pressure gas-refrigerant connection pipe 7, the low-pressure gas-refrigerant connection pipe 8, and the branch pipe portions 6 a, 6 b, 6 c, and 6 d), and the relay units 4 a, 4 b, 4 c, and 4 d, and constitutes part of the refrigerant circuit 10 as described above.

A configuration of the outdoor unit 2 is described next.

The outdoor unit 2 mainly includes a compressor 21 and at least one, in this case, two outdoor heat exchangers 23 a and 23 b. The compressor 21 is similar to the compressor 21 of the outdoor unit 2 according to one or more embodiments, and hence the description thereof is omitted. In addition, the outdoor unit 2 includes switching mechanisms 22 a and 22 b that switch the operating state between a radiation operating state in which the outdoor heat exchangers 23 a and 23 b function as radiators of the refrigerant, and an evaporation operating state in which the outdoor heat exchangers 23 a and 23 b function as evaporators of the refrigerant. The switching mechanisms 22 a and 22 b are connected to the suction side of the compressor 21 via a suction refrigerant pipe 31. The discharge side of the compressor 21 is connected to the switching mechanisms 22 a and 2 b via a discharge refrigerant pipe 32. The switching mechanism 22 a is connected to the gas-side ends of the outdoor heat exchangers 23 a and 23 b via first outdoor gas-refrigerant pipes 33 a and 33 b. The liquid sides of the outdoor heat exchangers 23 a and 23 b are connected to the liquid-refrigerant connection pipe 5 via an outdoor liquid-refrigerant pipe 34. The connection portion of the outdoor liquid-refrigerant pipe 34 with respect to the liquid-refrigerant connection pipe 5 is provided with a liquid-side shutoff valve 27. In addition, the outdoor unit 2 includes a third switching mechanism 22 c that switches the operating state between a refrigerant lead-out state in which the refrigerant discharged from the compressor 21 is sent to the high/low-pressure gas-refrigerant connection pipe 7, and a refrigerant lead-in state in which the refrigerant flowing through the high/low-pressure gas-refrigerant connection pipe 7 is sent to the suction refrigerant pipe 31. The third switching mechanism 22 c is connected to the high/low-pressure gas-refrigerant connection pipe 7 via a second outdoor gas-refrigerant pipe 35. The third switching mechanism 22 c is connected to the suction side of the compressor 21 via the suction refrigerant pipe 31. The discharge side of the compressor 21 is connected to the third switching mechanism 22 c via the discharge refrigerant pipe 32. The connection portion of the second outdoor gas-refrigerant pipe 35 with respect to the high/low-pressure gas-refrigerant connection pipe 7 is provided with a high/low-pressure gas-side shutoff valve 28 a. The suction refrigerant pipe 31 is connected to the low-pressure gas-refrigerant connection pipe 8. The connection portion of the suction refrigerant pipe 31 with respect to the low-pressure gas-refrigerant connection pipe 8 is provided with a low-pressure gas-side shutoff valve 28 b. The liquid-side shutoff valve 27 and the gas-side shutoff valves 28 a and 28 b are valves that are manually opened and closed.

The first switching mechanism 22 a is a device that can switch the flow of the refrigerant in the refrigerant circuit 10 such that, when the first outdoor heat exchanger 23 a functions as the radiator of the refrigerant (hereinafter, the situation is referred to as “outdoor radiation state”), the first switching mechanism 22 a connects the discharge side of the compressor 21 to the gas side of the first outdoor heat exchanger 23 a (see solid lines of the first switching mechanism 22 a in FIG. 9); and, when the first outdoor heat exchanger 23 a functions as the evaporator of the refrigerant (hereinafter, the situation is referred to as “outdoor evaporation state”), the first switching mechanism 22 a connects the suction side of the compressor 21 to the gas side of the first outdoor heat exchanger 23 a (see broken lines of the first switching mechanism 22 a in FIG. 9). The first switching mechanism 22 a is, for example, a four-way switching valve. The second switching mechanism 22 b is a device that can switch the flow of the refrigerant in the refrigerant circuit 10 such that, when the second outdoor heat exchanger 23 b functions as the radiator of the refrigerant (hereinafter, the situation is referred to as “outdoor radiation state”), the second switching mechanism 22 b connects the discharge side of the compressor 21 to the gas side of the second outdoor heat exchanger 23 b (see solid lines of the second switching mechanism 22 b in FIG. 9); and, when the second outdoor heat exchanger 23 b functions as the evaporator of the refrigerant (hereinafter, the situation is referred to as “outdoor evaporation state”), the second switching mechanism 22 b connects the suction side of the compressor 21 to the gas side of the second outdoor heat exchanger 23 b (see broken lines of the switching mechanism 22 in FIG. 9). The second switching mechanism 22 b is, for example, a four-way switching valve. By changing the switching states of the switching mechanisms 22 a and 22 b, the outdoor heat exchangers 23 a and 23 b can be individually switched to function as the evaporators or the radiators.

The first outdoor heat exchanger 23 a and the second outdoor heat exchanger 23 b are heat exchangers that exchange heat between the refrigerant, which is circulated among the outdoor unit 2 and the indoor units 3 a, 3 b, 3 c, and 3 d via the liquid-refrigerant connection pipe 5 and the gas-refrigerant connection pipe 6, and the outdoor air. The outdoor unit 2 includes an outdoor fan 24 that sucks the outdoor air into the outdoor unit 2, that causes the outdoor air to exchange heat with the refrigerant in the outdoor heat exchangers 23 a and 23 b, and then that discharges the outdoor air to the outside. That is, the outdoor unit 2 includes the outdoor fan 24 as a fan that sends the outdoor air, which serves as a cooling source or a heating source of the refrigerant flowing through the outdoor heat exchangers 23 a and 23 b, to the outdoor heat exchangers 23 a and 23 b. The outdoor fan 24 is driven by an outdoor fan motor 24 a.

The third switching mechanism 22 c is a device that can switch the flow of the refrigerant in the refrigerant circuit 10 such that, when the refrigerant discharged from the compressor 21 is sent to the high/low-pressure gas-refrigerant connection pipe 7 (hereinafter, the situation is referred to as “refrigerant lead-out state”), the third switching mechanism 22 c connects the discharge side of the compressor 21 to the high/low-pressure gas-refrigerant connection pipe 7 (see broken lines of the third switching mechanism 22 c in FIG. 9); and, when the refrigerant flowing through the high/low-pressure gas-refrigerant connection pipe 7 is sent to the suction refrigerant pipe 31 (hereinafter, the situation is referred to as “refrigerant lead-in state”), the third switching mechanism 22 c connects the suction side of the compressor 21 to the high/low-pressure gas-refrigerant connection pipe 7 (see solid lines of the third switching mechanism 22 c in FIG. 9). The third switching mechanism 22 c is, for example, a four-way switching valve.

Focusing on the outdoor heat exchangers 23 a and 23 b, the liquid-refrigerant connection pipe 5, the relay units 4 a, 4 b, 4 c, and 4 d, and the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d, the air conditioner 1 performs an operation (cooling only operation and cooling main operation) of circulating the refrigerant from the outdoor heat exchangers 23 a and 23 b, via the liquid-refrigerant connection pipe 5 and the relay units 4 a, 4 b, 4 c, and 4 d, to the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d that function as the evaporators of the refrigerant. The cooling only operation is an operating state in which only the indoor heat exchangers that function as the evaporators of the refrigerant (that is, the indoor units that perform cooling operation) exist. The cooling main operation is an operating state in which both the indoor heat exchanger that functions as the evaporator of the refrigerant and the indoor heat exchanger that functions as the radiator of the refrigerant (that is, the indoor unit that performs heating operation) are mixed; however, the load on the evaporation side (that is, cooling load) is relatively large as a whole. Focusing on the compressor 21, the gas-refrigerant connection pipe 6, the relay units 4 a, 4 b, 4 c, and 4 d, and the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d, the air conditioner 1 performs an operation (heating only operation and heating main operation) of circulating the refrigerant from the compressor 21, via the gas-refrigerant connection pipe 6 and the relay units 4 a, 4 b, 4 c, and 4 d, to the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d that function as the radiators of the refrigerant. The heating only operation is an operating state in which only the indoor heat exchangers that function as the radiators of the refrigerant (that is, the indoor units that perform heating operation) exist. The heating main operation is an operating state in which both the indoor heat exchanger that functions as the radiator of the refrigerant and the indoor heat exchanger that functions as the evaporator of the refrigerant are mixed; however, the load on the radiation side (that is, heating load) is relatively large as a whole. In cooling only operation and cooling main operation, at least one of the switching mechanisms 22 a and 22 b is switched to the outdoor radiation state. In this state, the outdoor heat exchangers 23 a and 23 b function as the radiators of the refrigerant as a whole, and the refrigerant flows from the outdoor unit 2 to the indoor units 3 a, 3 b, 3 c, and 3 d via the liquid-refrigerant connection pipe 5 and the relay units 4 a, 4 b, 4 c, and 4 d. In heating only operation and heating main operation, at least one of the switching mechanisms 22 a and 22 b is switched to the outdoor evaporation state and the third switching mechanism 22 c is switched to the refrigerant lead-out state. In this state, the outdoor heat exchangers 23 a and 23 b function as the evaporators of the refrigerant as a whole, and the refrigerant flows from the indoor units 3 a, 3 b, 3 c, and 3 d to the outdoor unit 2 via the liquid-refrigerant connection pipe 5 and the relay units 4 a, 4 b, 4 c, and 4 d.

In addition, outdoor expansion valves 25 a and 25 b and a liquid-pressure adjustment expansion valve 26 are provided in the outdoor liquid-refrigerant pipe 34. The outdoor expansion valves 25 a and 25 b are electric expansion valves that decompress the refrigerant in heating only operation and heating main operation, and are provided in portions of the outdoor liquid-refrigerant pipe 34 near the liquid sides of the outdoor heat exchangers 23 a and 23 b. The liquid-pressure adjustment expansion valve 26 is an electric expansion valve that decompresses the refrigerant so that the refrigerant flowing through the liquid-refrigerant connection pipe 5 is brought into a gas-liquid two-phase state in cooling only operation and cooling main operation, and is provided in a portion of the outdoor liquid-refrigerant pipe 34 near the liquid-refrigerant connection pipe 5. That is, the liquid-pressure adjustment expansion valve 26 is provided in a portion of the outdoor liquid-refrigerant pipe 34 nearer to the liquid-refrigerant connection pipe 5 than the outdoor expansion valves 25 a and 25 b.

The air conditioner 1 performs two-phase refrigerant feed of sending the refrigerant in the gas-liquid two-phase state to the liquid-refrigerant connection pipe 5 by the liquid-pressure adjustment expansion valve 26 and hence sending the refrigerant from the outdoor unit 2 to the indoor units 3 a, 3 b, 3 c, and 3 d in cooling only operation and cooling main operation.

Furthermore, a refrigerant return pipe 41 is connected to the outdoor liquid-refrigerant pipe 34, and a refrigerant cooler 45 is provided. The refrigerant return pipe 41 and the refrigerant cooler 45 are similar to the refrigerant return pipe 41 and the refrigerant cooler 45 of the outdoor unit 2 according to one or more embodiments, and hence the description thereof is omitted.

The outdoor unit 2 is provided with various sensors. To be specific, the outdoor unit 2 is provided with a discharge pressure sensor 36 that detects a pressure (discharge pressure Pd) of the refrigerant discharged from the compressor 21. In addition, the outdoor unit 2 is provided with outdoor heat-exchange liquid-side sensors 37 a and 37 b that detect temperatures Tol (outdoor heat-exchange outlet temperatures Tol) of the refrigerant on the liquid sides of the outdoor heat exchangers 23 a and 23 b, and is provided with a liquid-pipe temperature sensor 38 that detects a temperature (liquid-pipe temperature Tlp) of the refrigerant in a portion of the outdoor liquid-refrigerant pipe 34 between the refrigerant cooler 45 and the liquid-pressure adjustment expansion valve 26.

Relay Unit

The relay units 4 a, 4 b, 4 c, and 4 d are arranged in the building or the like. In this case, the relay units 4 a, 4 b, 4 c, and 4 d are arranged outside the air-conditioning target spaces unlike the indoor units 3 a, 3 b, 3 c, and 3 d. The relay units 4 a, 4 b, 4 c, and 4 d are connected between the indoor units 3 a, 3 b, 3 c, and 3 d and the outdoor unit 2, together with the liquid-refrigerant connection pipe 5, the gas-refrigerant connection pipe 6 (the high/low-pressure gas-refrigerant connection pipe 7, the low-pressure gas-refrigerant connection pipe 8, and the branch pipe portions 6 a, 6 b, 6 c, and 6 d), and constitute part of the refrigerant circuit 10.

Configurations of the relay units 4 a, 4 b, 4 c, and 4 d are described next. The relay unit 4 a and the relay units 4 b, 4 c, and 4 d have configurations similar to one another. Hence only the configuration of the relay unit 4 a is described. For the configurations of the relay units 4 b, 4 c, and 4 d, the description of the components of the relay units 4 b, 4 c, and 4 d is omitted while an index “b”, “c”, or “d” is applied to each component instead of the index “a” indicating each component of the relay unit 4 a.

The relay unit 4 a mainly includes a liquid connection pipe 61 a and a gas connection pipe 62 a.

One end of the liquid connection pipe 61 a is connected to the first branch pipe portion 5 a of the liquid-refrigerant connection pipe 5. The other end of the liquid connection pipe 61 a is connected to the second branch pipe portion 5 aa of the liquid-refrigerant connection pipe 5.

The liquid connection pipe 61 a is connected to a portion of the liquid-refrigerant connection pipe 5 on the side of the indoor unit 3 a (in this case, the second branch pipe portion 5 aa) by mechanical pipe joint, such as flare connection (the portion of the mechanical pipe joint is referred to as pipe joint portion 98 a). The pipe joint portion 98 a is connected to the liquid connection pipe 61 a by brazing (the brazing portion is referred to as brazing portion 98 aa). Although not illustrated here, the liquid connection pipe 61 a may be directly connected to the liquid-refrigerant connection pipe 5 (in this case, the second branch pipe portion 5 aa) by brazing. The liquid connection pipe 61 a is connected to a portion of the liquid-refrigerant connection pipe 5 on the side of the outdoor unit 2 (in this case, the first branch pipe portion 5 a) by mechanical pipe joint, such as flare connection (the portion of the mechanical pipe joint is referred to as pipe joint portion 99 a). The pipe joint portion 99 a is connected to the liquid connection pipe 61 a by brazing (the brazing portion is referred to as brazing portion 99 aa). Although not illustrated here, the liquid connection pipe 61 a may be directly connected to the liquid-refrigerant connection pipe 5 (in this case, the first branch pipe portion 5 a) by brazing.

The gas connection pipe 62 a includes a high-pressure gas connection pipe 63 a connected to the branch pipe portion 7 a of the high/low-pressure gas-refrigerant connection pipe 7, a low-pressure gas connection pipe 64 a connected to the branch pipe portion 8 a of the low-pressure gas-refrigerant connection pipe 8, and a joint gas connection pipe 65 a that joins the high-pressure gas connection pipe 63 a and the low-pressure gas connection pipe 64 a together. The joint gas connection pipe 65 a is connected to the branch pipe portion 6 a of the gas-refrigerant connection pipe 6. The high-pressure gas connection pipe 63 a is provided with a first cooling/heating switching valve 58 a. The low-pressure gas connection pipe 64 a is provided with a second cooling/heating switching valve 59 a. The first cooling/heating switching valve 58 a and the second cooling/heating switching valve 59 a are electric expansion valves. The first cooling/heating switching valve 58 a and the second cooling/heating switching valve 59 a may not be electric expansion valves and may be electromagnetic valves.

The relay unit 4 a can function such that, when the indoor unit 3 a performs cooling operation, the second cooling/heating switching valve 59 a is opened to allow the refrigerant to flow into the liquid connection pipe 61 a via the first branch pipe portion 5 a of the liquid-refrigerant connection pipe 5, the refrigerant is sent to the indoor unit 3 a via the second branch pipe portion 5 aa of the liquid-refrigerant connection pipe 5, then the refrigerant evaporated through heat exchange with the indoor air in the indoor heat exchanger 52 a is recovered to the branch pipe portion 8 a of the low-pressure gas-refrigerant connection pipe 8 via the branch pipe portion 6 a of the gas-refrigerant connection pipe 6, the joint gas connection pipe 65 a, and the low-pressure gas connection pipe 64 a. In addition, the relay unit 4 a can function such that, when the indoor unit 3 a performs heating operation, the second cooling/heating switching valve 59 a is closed and the first cooling/heating switching valve 58 a is opened to allow the refrigerant to flow into the high-pressure gas connection pipe 63 a and the joint gas connection pipe 65 a via the branch pipe portion 7 a of the high/low-pressure gas-refrigerant connection pipe 7, the refrigerant is sent to the indoor unit 3 a via the branch pipe portion 6 a of the gas-refrigerant connection pipe 6, then the refrigerant radiated through heat exchange with the indoor air in the indoor heat exchanger 52 a is recovered to the first branch pipe portion 5 a of the liquid-refrigerant connection pipe 5 via the second branch pipe portion 5 aa of the liquid-refrigerant connection pipe 5 and the liquid connection pipe 61 a. The first cooling/heating switching valve 58 a and the second cooling/heating switching valve 59 a are opened and closed through switching to cause the indoor heat exchanger 52 a to function as the evaporator of the refrigerant or the radiator of the refrigerant. Not only the relay unit 4 a but also the relay units 4 b, 4 c, and 4 d have such a function. With the relay units 4 a, 4 b, 4 c, and 4 d, the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d can be individually switched to function as the evaporators of the refrigerant or the radiators of the refrigerant.

The high-pressure gas connection pipe 63 a mainly includes an indoor-side high-pressure gas connection pipe 66 a that is connected to a portion of the gas-refrigerant connection pipe 6 on the side of the indoor unit 3 a (in this case, the branch pipe portion 6 a) via the joint gas connection pipe 65 a, and an outdoor-side high-pressure gas connection pipe 67 a that is connected to a portion of the gas-refrigerant connection pipe 6 on the side of the outdoor unit 2 (in this case, the branch pipe portion 7 a of the high/low-pressure gas-refrigerant connection pipe 7). The first cooling/heating switching valve 58 a is connected to the indoor-side high-pressure gas connection pipe 66 a by brazing (the brazing portion is referred to as brazing portion 91 a). The first cooling/heating switching valve 58 a is connected to the outdoor-side high-pressure gas connection pipe 67 a by brazing (the brazing portion is referred to as brazing portion 92 a). The low-pressure gas connection pipe 64 a mainly includes an indoor-side low-pressure gas connection pipe 68 a that is connected to a portion of the gas-refrigerant connection pipe 6 on the side of the indoor unit 3 a (in this case, the branch pipe portion 6 a) via the joint gas connection pipe 65 a, and an outdoor-side low-pressure gas connection pipe 69 a that is connected to a portion of the gas-refrigerant connection pipe 6 on the side of the outdoor unit 2 (in this case, the branch pipe portion 8 a of the low-pressure gas-refrigerant connection pipe 8). The second cooling/heating switching valve 59 a is connected to the indoor-side low-pressure gas connection pipe 68 a by brazing (the brazing portion is referred to as brazing portion 93 a). The second cooling/heating switching valve 59 a is connected to the outdoor-side low-pressure gas connection pipe 69 a by brazing (the brazing portion is referred to as brazing portion 94 a). The joint gas connection pipe 65 a is connected to a portion of the gas-refrigerant connection pipe 6 on the side of the indoor unit 3 a (in this case, the branch pipe portion 6 a) by mechanical pipe joint, such as flare connection (the portion of the mechanical pipe joint is referred to as pipe joint portion 95 a). The pipe joint portion 95 a is connected to the joint gas connection pipe 65 a by brazing (the brazing portion is referred to as brazing portion 95 aa). Although not illustrated here, the joint gas connection pipe 65 a may be directly connected to the gas-refrigerant connection pipe 6 (in this case, the branch pipe portion 6 a) by brazing. The outdoor-side high-pressure gas connection pipe 67 a is connected to a portion of the gas-refrigerant connection pipe 6 on the side of the outdoor unit 2 (in this case, the branch pipe portion 7 a of the high/low-pressure gas-refrigerant connection pipe 7) by mechanical pipe joint, such as flare connection (the portion of the mechanical pipe joint is referred to as pipe joint portion 96 a). The pipe joint portion 96 a is connected to the outdoor-side high-pressure gas connection pipe 67 a by brazing (the brazing portion is referred to as brazing portion 96 aa). Although not illustrated here, the outdoor-side high-pressure gas connection pipe 67 a may be directly connected to the gas-refrigerant connection pipe 6 (in this case, the branch pipe portion 7 a of the high/low-pressure gas-refrigerant connection pipe 7) by brazing. The outdoor-side low-pressure gas connection pipe 69 a is connected to a portion of the gas-refrigerant connection pipe 6 on the side of the outdoor unit 2 (in this case, the branch pipe portion 8 a of the low-pressure gas-refrigerant connection pipe 8) by mechanical pipe joint, such as flare connection (the portion of the mechanical pipe joint is referred to as pipe joint portion 97 a). The pipe joint portion 97 a is connected to the outdoor-side low-pressure gas connection pipe 69 a by brazing (the brazing portion is referred to as brazing portion 97 aa). Although not illustrated here, the outdoor-side low-pressure gas connection pipe 69 a may be directly connected to the gas-refrigerant connection pipe 6 (in this case, the branch pipe portion 8 a of the low-pressure gas-refrigerant connection pipe 8) by brazing.

Control Unit

The control unit 19 is constituted by being connected to control boards or the like (not illustrated) provided in, for example, the outdoor unit 2, the indoor units 3 a, 3 b, 3 c, and 3 d, and the relay units 4 a, 4 b, 4 c, and 4 d to communicate therewith. In FIG. 9, however, the control unit 19 is illustrated at a position separated from the outdoor unit 2, the indoor units 3 a, 3 b, 3 c, and 3 d, and the relay units 4 a, 4 b, 4 c, and 4 d for the convenience of illustration. The control unit 19 controls the components 21, 22, 24, 25 a, 25 b, 26, 44, 51 a to 51 d, 55 a to 55 d, 58 a to 58 d, and 59 a to 59 d of the air conditioner 1 (in this case, the outdoor unit 2, the indoor units 3 a, 3 b, 3 c, and 3 d, and the relay units 4 a, 4 b, 4 c, and 4 d), that is, controls the entire operation of the air conditioner 1 in accordance with the detection signals of the above-described various sensors 36, 37 a, 37 b, 38, 57 a, 57 b, 57 c, and 57 d.

Operation without Leakage of Refrigerant

The operation of the air conditioner 1 when the refrigerant does not leak is described next with reference to FIG. 9. The air conditioner 1 performs cooling only operation, heating only operation, cooling main operation, and heating main operation. The air conditioner 1 performs two-phase refrigerant feed of sending the refrigerant in the gas-liquid two-phase state to the liquid-refrigerant connection pipe 5 by the liquid-pressure adjustment expansion valve 26 provided in the outdoor liquid-refrigerant pipe 34 and hence sending the refrigerant from the outdoor unit 2 to the indoor units 3 a, 3 b, 3 c, and 3 d in cooling operation and cooling main operation. The operation of the air conditioner 1 which is described below is performed by the control unit 19 that controls the components of the air conditioner 1.

Cooling Only Operation

In cooling only operation, for example, when all the indoor units 3 a, 3 b, 3 c, and 3 d perform cooling operation (that is, operation in which all the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d function as the evaporators of the refrigerant and the outdoor heat exchangers 23 a and 23 b function as the radiators of the refrigerant), the switching mechanisms 22 a and 22 b are switched to the outdoor radiation state (the state in which the switching mechanisms 22 a and 22 b are indicated by solid lines in FIG. 9), and the compressor 21, the outdoor fan 24, and the indoor fans 55 a, 55 b, 55 c, and 55 d are driven. In addition, the third switching mechanism 22 c is switched to the refrigerant lead-in state (the state in which the switching mechanism 22 c is indicated by solid lines in FIG. 9), and the first cooling/heating switching valves 58 a, 58 b, 58 c, and 58 d and the second cooling/heating switching valves 59 a, 59 b, 59 c, and 59 d of the relay units 4 a, 4 b, 4 c, and 4 d are opened.

Then, the high-pressure refrigerant discharged from the compressor 21 is sent to the outdoor heat exchangers 23 a and 23 b via the switching mechanisms 22 a and 22 b. The refrigerant sent to the outdoor heat exchangers 23 a and 23 b is condensed by being cooled through heat exchange with the outdoor air supplied by the outdoor fan 24 in the outdoor heat exchangers 23 a and 23 b that function as the radiators of the refrigerant. The refrigerant flows out from the outdoor unit 2 via the outdoor expansion valves 25 a and 25 b, the refrigerant cooler 45, the liquid-pressure adjustment expansion valve 26, and the liquid-side shutoff valve 27.

The refrigerant flowing out from the outdoor unit 2 is branched and sent to the relay units 4 a, 4 b, 4 c, and 4 d via the liquid-refrigerant connection pipe 5 (the joint pipe portion and the first branch pipe portions 5 a, 5 b, 5 c, and 5 d). The refrigerant sent to the relay units 4 a, 4 b, 4 c, and 4 d is sent to the indoor units 3 a, 3 b, 3 c, and 3 d. The refrigerant sent to the indoor units 3 a, 3 b, 3 c, and 3 d is decompressed by the indoor expansion valves 51 a, 51 b, 51 c, and 51 d and then sent to the indoor heat exchangers 52 a, 52 b, 52 a, and 52 b. The refrigerant sent to the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d is evaporated by being heated through heat exchange with the indoor air supplied from the air-conditioning target spaces by the indoor fans 55 a, 55 b, 55 c, and 55 d in the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d that function as the evaporators of the refrigerant. The refrigerant flows out from the indoor units 3 a, 3 b, 3 c, and 3 d. The indoor air cooled by the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d is sent to the air-conditioning target spaces and the air-conditioning target spaces are cooled by using the cooled indoor air.

The refrigerant flowing out from the indoor units 3 a, 3 b, 3 c, and 3 d is sent to the relay units 4 a, 4 b, 4 c, and 4 d via the branch pipe portions 6 a, 6 b, 6 c, and 6 d of the gas-refrigerant connection pipe 6. The refrigerant sent to the relay units 4 a, 4 b, 4 c, and 4 d flows out from the relay units 4 a, 4 b, 4 c, and 4 d via the first cooling/heating switching valves 58 a, 58 b, 58 c, and 58 d and the second cooling/heating switching valves 59 a, 59 b, 59 c, and 59 d.

The refrigerant flowing out from the relay units 4 a, 4 b, 4 c, and 4 d is joined and sent to the outdoor unit 2 via the high/low-pressure gas-refrigerant connection pipe 7 (the joint pipe portion and the branch pipe portions 7 a, 7 b, 7 c, and 7 d) and the low-pressure gas-refrigerant connection pipe 8 (the joint pipe portion and the branch pipe portions 8 a, 8 b, 8 c, and 8 d). The refrigerant sent to the outdoor unit 2 is sucked into the compressor 21 via the gas-side shutoff valves 28 a and 28 b and the third switching mechanism 22 c.

In the above-described cooling only operation, the air conditioner 1 performs two-phase refrigerant feed of sending the refrigerant in the gas-liquid two-phase state to the liquid-refrigerant connection pipe 5 by the liquid-pressure adjustment expansion valve 26 and hence sending the refrigerant from the outdoor unit 2 to the indoor units 3 a, 3 b, 3 c, and 3 d. In addition, the refrigerant flowing through the outdoor liquid-refrigerant pipe 34 is cooled by the refrigerant return pipe 41 and the refrigerant cooler 45 to reduce variation in the liquid-pipe temperature Tlp in the portion of the outdoor liquid-refrigerant pipe 34 between the refrigerant cooler 45 and the liquid-pressure adjustment expansion valve 26, so that the two-phase refrigerant feed can be properly performed. The control content relating to the two-phase refrigerant feed is similar to the control content relating to the two-phase refrigerant feed by the air conditioner 1 according to one or more embodiments, and hence the description thereof is omitted. With this control, the refrigerant flowing through the liquid-refrigerant connection pipe 5 is brought into the gas-liquid two-phase state. Hence, the liquid-refrigerant connection pipe 5 is less likely filled with the refrigerant in the liquid state as compared with the case where the refrigerant flowing through the liquid-refrigerant connection pipe 5 is in the liquid state. The amount of refrigerant existing in the liquid-refrigerant connection pipe 5 can be decreased by that amount. By making the liquid-pipe temperature Tlp constant and reducing variation, the refrigerant flowing through the liquid-refrigerant connection pipe 5 after decompressed by the liquid-pressure adjustment expansion valve 26 can be reliably maintained in a desirable gas-liquid two-phase state.

Heating Only Operation

In heating only operation, for example, when all the indoor units 3 a, 3 b, 3 c, and 3 d perform heating operation (that is, operation in which all the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d function as the radiators of the refrigerant and the outdoor heat exchangers 23 a and 23 b function as the evaporators of the refrigerant), the switching mechanisms 22 a and 22 b are switched to the outdoor evaporation state (the state in which the switching mechanisms 22 a and 22 b are indicated by broken lines in FIG. 9), and the compressor 21, the outdoor fan 24, and the indoor fans 55 a, 55 b, 55 c, and 55 d are driven. In addition, the third switching mechanism 22 c is switched to the refrigerant lead-out state (the state in which the switching mechanism 22 c is indicated by broken lines in FIG. 9), and the first cooling/heating switching valves 58 a, 58 b, 58 c, and 58 d and the second cooling/heating switching valves 59 a, 59 b, 59 c, and 59 d of the relay units 4 a, 4 b, 4 c, and 4 d are closed.

Then, the high-pressure refrigerant discharged from the compressor 21 flows out from the outdoor unit 2 via the third switching mechanism 22 c and the gas-side shutoff valve 28 a.

The refrigerant flowing out from the outdoor unit 2 is branched and sent to the relay units 4 a, 4 b, 4 c, and 4 d via the gas-refrigerant connection pipe 6 (the joint pipe portion and the branch pipe portions 7 a, 7 b, 7 c, and 7 d of the high/low-pressure gas-refrigerant connection pipe 7). The refrigerant sent to the relay units 4 a, 4 b, 4 c, and 4 d flows out from the relay units 4 a, 4 b, 4 c, and 4 d via the first cooling/heating switching valves 58 a, 58 b, 58 c, and 58 d.

The refrigerant flowing out from the relay units 4 a, 4 b, 4 c, and 4 d is sent to the indoor units 3 a, 3 b, 3 c, and 3 d via the branch pipe portions 6 a, 6 b, 6 c, and 6 d (the portions of the gas-refrigerant connection pipe 6 connecting the relay units 4 a, 4 b, 4 c, and 4 d to the indoor units 3 a, 3 b, 3 c, and 3 d). The refrigerant sent to the indoor units 3 a, 3 b, 3 c, and 3 d is sent to the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d. The high-pressure refrigerant sent to the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d is condensed by being cooled through heat exchange with the indoor air supplied from the air-conditioning target spaces by the indoor fans 55 a, 55 b, 55 c, and 55 d in the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d that function as the radiators of the refrigerant. The refrigerant is decompressed by the indoor expansion valves 51 a, 51 b, 51 c, and 51 d and then flows out from the indoor units 3 a, 3 b, 3 c, and 3 d. The indoor air heated by the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d is sent to the air-conditioning target spaces and the air-conditioning target spaces are heated by using the heated indoor air.

The refrigerant flowing out from the indoor units 3 a, 3 b, 3 c, and 3 d is sent to the relay units 4 a, 4 b, 4 c, and 4 d via the second branch pipe portions 5 aa, 5 bb, 5 cc, and 5 dd (the portions of the liquid-refrigerant connection pipe 5 connecting the relay units 4 a, 4 b, 4 c, and 4 d to the indoor units 3 a, 3 b, 3 c, and 3 d). The refrigerant sent to the relay units 4 a, 4 b, 4 c, and 4 d flows out from the relay units 4 a, 4 b, 4 c, and 4 d.

The refrigerant flowing out from the relay units 4 a, 4 b, 4 c, and 4 d is joined and sent to the outdoor unit 2 via the liquid-refrigerant connection pipe 5 (the joint pipe portion and the first branch pipe portions 5 a, 5 b, 5 c, and 5 d). The refrigerant sent to the outdoor unit 2 is sent to the outdoor expansion valves 25 a and 25 b via the liquid-side shutoff valve 27 and the refrigerant cooler 45. The refrigerant sent to the outdoor expansion valves 25 a and 25 b is decompressed by the outdoor expansion valves 25 a and 25 b and then is sent to the outdoor heat exchangers 23 a and 23 b. The refrigerant sent to the outdoor heat exchangers 23 a and 23 b is evaporated by being heated through heat exchange with the outdoor air supplied by the outdoor fan 24. The refrigerant is sucked into the compressor 21 via the switching mechanisms 22 a and 22 b.

In the above-described heating only operation, unlike cooling only operation, the control unit 19 performs control to fix the opening degree of the liquid-pressure adjustment expansion valve 26 in a fully opened state. Thus, the opening degree of the refrigerant return expansion valve 44 is brought into a fully closed state to inhibit the refrigerant from flowing to the refrigerant return pipe 41.

Cooling Main Operation

In cooling main operation, for example, when the indoor units 3 b, 3 c, and 3 d perform cooling operation, the indoor unit 3 a performs heating operation (that is, operation in which the indoor heat exchangers 52 b, 52 c, and 52 d function as the evaporators of the refrigerant and the indoor heat exchanger 52 a functions as the radiator of the refrigerant), and the indoor heat exchangers 23 a and 23 b function as the radiators of the refrigerant, the switching mechanisms 22 a and 22 b are switched to the outdoor radiation state (the state in which the switching mechanisms 22 a and 22 b are indicated by solid lines in FIG. 9), and the compressor 21, the outdoor fan 24, and the indoor fans 55 a, 55 b, 55 c, and 55 d are driven. In addition, the third switching mechanism 22 c is switched to the refrigerant lead-out state (the state in which the switching mechanism 22 c is indicated by broken lines in FIG. 9), the first cooling/heating switching valve 58 a of the relay unit 4 a and the second cooling/heating switching valves 59 b, 59 c, and 59 d of the relay units 4 b, 4 c, and 4 d are opened, and the second cooling/heating switching valve 59 a of the relay unit 4 a as well as the first cooling/heating switching valves 58 b 58 c, and 58 d of the relay units 4 b, 4 c, and 4 d are closed.

Then, part of the high-pressure refrigerant discharged from the compressor 21 is sent to the outdoor heat exchangers 23 a and 23 b via the switching mechanisms 22 a and 22 b, and the residual part of the high-pressure refrigerant flows out from the outdoor unit 2 via the third switching mechanism 22 c and the gas-side shutoff valve 28 a. The refrigerant sent to the outdoor heat exchangers 23 a and 23 b is condensed by being cooled through heat exchange with the outdoor air supplied by the outdoor fan 24 in the outdoor heat exchangers 23 a and 23 b that function as the radiators of the refrigerant. The refrigerant flows out from the outdoor unit 2 via the outdoor expansion valves 25 a and 25 b, the refrigerant cooler 45, the liquid-pressure adjustment expansion valve 26, and the liquid-side shutoff valve 27.

The refrigerant flowing out from the outdoor unit 2 via the third switching mechanism 22 c and so forth is sent to the relay unit 4 a via the gas-refrigerant connection pipe 6 (the joint pipe portion and the branch pipe portion 7 a of the high/low-pressure gas-refrigerant connection pipe 7). The refrigerant sent to the relay unit 4 a flows out from the relay unit 4 a via the first cooling/heating switching valve 58 a.

The refrigerant flowing out from the relay unit 4 a is sent to the indoor unit 3 a via the branch pipe portion 6 a (the portion of the gas-refrigerant connection pipe 6 connecting the relay unit 4 a to the indoor unit 3 a). The refrigerant sent to the indoor unit 3 a is sent to the indoor heat exchanger 52 a. The high-pressure refrigerant sent to the indoor heat exchanger 52 a is condensed by being cooled through heat exchange with the indoor air supplied from the air-conditioning target space by the indoor fan 55 a in the indoor heat exchanger 52 a that functions as the radiator of the refrigerant. The refrigerant is decompressed by the indoor expansion valve 51 a and then flows out from the indoor unit 3 a. The indoor air heated by the indoor heat exchanger 52 a is sent to the air-conditioning target space and the air-conditioning target space is heated by using the heated indoor air.

The refrigerant flowing out from the indoor unit 3 a is sent to the relay unit 4 a via the second branch pipe portion 5 aa (the portion of the liquid-refrigerant connection pipe 5 connecting the relay unit 4 a to the indoor unit 3 a). The refrigerant sent to the relay unit 4 a flows out from the relay unit 4 a.

The refrigerant flowing out from the relay unit 4 a is sent to the joint pipe portion of the liquid-refrigerant connection pipe 5 via the first branch pipe portion 5 a, and is joined to the refrigerant flowing out from the outdoor unit 2 via the outdoor heat exchangers 23 a and 23 b. The refrigerant is branched and sent to the relay units 4 b, 4 c, and 4 d via the first branch pipe portions 5 b, 5 c, and 5 d of the liquid-refrigerant connection pipe 5. The refrigerant sent to the relay units 4 b, 4 c, and 4 d flows out from the relay units 4 b, 4 c, and 4 d.

The refrigerant flowing out from the relay units 4 b, 4 c, and 4 d is sent to the indoor units 3 b, 3 c, and 3 d via the second branch pipe portions 5 bb, 5 cc, and 5 dd (the portions of the liquid-refrigerant connection pipe 5 connecting the relay units 4 b, 4 c, and 4 d to the indoor units 3 b, 3 c, and 3 d). The refrigerant sent to the indoor units 3 b, 3 c, and 3 d is decompressed by the indoor expansion valves 51 b, 51 c, and 51 d and then sent to the indoor heat exchangers 52 b, 52 a, and 52 b. The refrigerant sent to the indoor heat exchangers 52 b, 52 c, and 52 d is evaporated by being heated through heat exchange with the indoor air supplied from the air-conditioning target spaces by the indoor fans 55 b, 55 c, and 55 d in the indoor heat exchangers 52 b, 52 c, and 52 d that function as the evaporators of the refrigerant. The refrigerant flows out from the indoor units 3 b, 3 c, and 3 d. The indoor air cooled by the indoor heat exchangers 52 b, 52 c, and 52 d is sent to the air-conditioning target spaces and the air-conditioning target spaces are cooled by using the cooled indoor air.

The refrigerant flowing out from the indoor units 3 b, 3 c, and 3 d is sent to the relay units 4 b, 4 c, and 4 d via the branch pipe portions 6 b, 6 c, and 6 d of the gas-refrigerant connection pipe 6. The refrigerant sent to the relay units 4 b, 4 c, and 4 d flows out from the relay units 4 b, 4 c, and 4 d via the second cooling/heating switching valves 59 b, 59 c, and 59 d.

The refrigerant flowing out from the relay units 4 b, 4 c, and 4 d is joined and sent to the outdoor unit 2 via the low-pressure gas-refrigerant connection pipe 8 (the joint pipe portion and the branch pipe portions 8 b, 8 c, and 8 d). The refrigerant sent to the outdoor unit 2 is sucked into the compressor 21 via the gas-side shutoff valves 28 a and 28 b and the third switching mechanism 22 c.

In the above-described cooling main operation, like cooling only operation, the air conditioner 1 performs two-phase refrigerant feed of sending the refrigerant in the gas-liquid two-phase state to the liquid-refrigerant connection pipe 5 by the liquid-pressure adjustment expansion valve 26 and hence sending the refrigerant from the outdoor unit 2 to the indoor units 3 a, 3 b, 3 c, and 3 d. In addition, the refrigerant flowing through the outdoor liquid-refrigerant pipe 34 is cooled by the refrigerant return pipe 41 and the refrigerant cooler 45 to reduce variation in the liquid-pipe temperature Tlp in the portion of the outdoor liquid-refrigerant pipe 34 between the refrigerant cooler 45 and the liquid-pressure adjustment expansion valve 26, so that the two-phase refrigerant feed can be properly performed.

Heating Main Operation

In heating main operation, for example, when the indoor units 3 b, 3 c, and 3 d perform heating operation, the indoor unit 3 a performs cooling operation (that is, operation in which the indoor heat exchangers 52 b, 52 c, and 52 d function as the radiators of the refrigerant and the indoor heat exchanger 52 a functions as the evaporator of the refrigerant), and the indoor heat exchangers 23 a and 23 b function as the evaporators of the refrigerant, the switching mechanisms 22 a and 22 b are switched to the outdoor evaporation state (the state in which the switching mechanisms 22 a and 22 b are indicated by solid lines in FIG. 9), and the compressor 21, the outdoor fan 24, and the indoor fans 55 a, 55 b, 55 c, and 55 d are driven. In addition, the third switching mechanism 22 c is switched to the refrigerant lead-out state (the state in which the switching mechanism 22 c is indicated by broken lines in FIG. 9), the second cooling/heating switching valves 59 b, 59 c, and 59 d of the relay units 4 b, 4 c, and 4 d are closed, and the second cooling/heating switching valve 59 a of the relay unit 4 a as well as the first cooling/heating switching valves 58 b 58 c, and 58 d of the relay units 4 b, 4 c, and 4 d are opened.

Then, the high-pressure refrigerant discharged from the compressor 21 flows out from the outdoor unit 2 via the third switching mechanism 22 c and the gas-side shutoff valve 28 a.

The refrigerant flowing out from the outdoor unit 2 is branched and sent to the relay units 4 b, 4 c, and 4 d via the gas-refrigerant connection pipe 6 (the joint pipe portion and the branch pipe portions 7 b, 7 c, and 7 d of the high/low-pressure gas-refrigerant connection pipe 7). The refrigerant sent to the relay units 4 b, 4 c, and 4 d flows out from the relay units 4 b, 4 c, and 4 d via the first cooling/heating switching valves 58 b, 58 c, and 58 d.

The refrigerant flowing out from the relay units 4 b, 4 c, and 4 d is sent to the indoor units 3 b, 3 c, and 3 d via the branch pipe portions 6 b, 6 c, and 6 d (the portions of the gas-refrigerant connection pipe 6 connecting the relay units 4 b, 4 c, and 4 d to the indoor units 3 b, 3 c, and 3 d). The refrigerant sent to the indoor units 3 b, 3 c, and 3 d is sent to the indoor heat exchangers 52 b, 52 c, and 52 d. The high-pressure refrigerant sent to the indoor heat exchangers 52 b, 52 c, and 52 d is condensed by being cooled through heat exchange with the indoor air supplied from the air-conditioning target spaces by the indoor fans 55 b, 55 c, and 55 d in the indoor heat exchangers 52 b, 52 c, and 52 d that function as the radiators of the refrigerant. The refrigerant is decompressed by the indoor expansion valves 51 b, 51 c, and 51 d and then flows out from the indoor units 3 b, 3 c, and 3 d. The indoor air heated by the indoor heat exchangers 52 b, 52 c, and 52 d is sent to the air-conditioning target spaces and the air-conditioning target spaces are heated by using the heated indoor air.

The refrigerant flowing out from the indoor units 3 b, 3 c, and 3 d is sent to the relay units 4 b, 4 c, and 4 d via the second branch pipe portions 5 bb, 5 cc, and 5 dd (the portions of the liquid-refrigerant connection pipe 5 connecting the relay units 4 b, 4 c, and 4 d to the indoor units 3 b, 3 c, and 3 d). The refrigerant sent to the relay units 4 b, 4 c, and 4 d flows out from the relay units 4 b, 4 c, and 4 d.

The refrigerant flowing out from the relay units 4 a, 4 b, 4 c, and 4 d is joined to the joint pipe portion via the first branch pipe portions 5 a, 5 b, 5 c, and 5 d of the liquid-refrigerant connection pipe 5, part of the refrigerant is branched to the first branch pipe portion 5 a and sent to the relay unit 4 a, and the residual part of the refrigerant is sent to the outdoor unit 2 via the joint pipe portion of the liquid-refrigerant connection pipe 5. The refrigerant sent to the relay unit 4 a flows out from the relay unit 4 a.

The refrigerant flowing out from the relay unit 4 a is sent to the indoor unit 3 a via the second branch pipe portion 5 aa (the portion of the liquid-refrigerant connection pipe 5 connecting the relay unit 4 a to the indoor unit 3 a). The refrigerant sent to the indoor units 3 a is decompressed by the indoor expansion valve 51 a and then sent to the indoor heat exchanger 52 a. The refrigerant sent to the indoor heat exchanger 52 a is evaporated by being heated through heat exchange with the indoor air supplied from the air-conditioning target space by the indoor fan 55 a in the indoor heat exchanger 52 a that functions as the evaporator of the refrigerant. The refrigerant flows out from the indoor unit 3 a. The indoor air cooled by the indoor heat exchanger 52 a is sent to the air-conditioning target space and the air-conditioning target space is cooled by using the cooled indoor air.

The refrigerant flowing out from the indoor unit 3 a is sent to the relay unit 4 a via the branch pipe portion 6 a of the gas-refrigerant connection pipe 6. The refrigerant sent to the relay unit 4 a flows out from the relay unit 4 a via the second cooling/heating switching valve 59 a.

The refrigerant flowing out from the relay unit 4 a is sent to the outdoor unit 2 via the low-pressure gas-refrigerant connection pipe 8 (the joint pipe portion and the branch pipe portion 8 a). The refrigerant sent to the outdoor unit 2 via the joint pipe portion of the liquid-refrigerant connection pipe 5 is sent to the outdoor expansion valves 25 a and 25 b via the liquid-side shutoff valve 27, the liquid-pressure adjustment expansion valve 26, and the refrigerant cooler 45. The refrigerant sent to the outdoor expansion valves 25 a and 25 b is decompressed by the outdoor expansion valves 25 a and 25 b and then is sent to the outdoor heat exchangers 23 a and 23 b. The refrigerant sent to the outdoor heat exchangers 23 a and 23 b is evaporated by being heated through heat exchange with the outdoor air supplied by the outdoor fan 24. The refrigerant is joined to the refrigerant sent to the outdoor unit 2 via the low-pressure gas-refrigerant connection pipe 8 and is sucked into the compressor 21, via the switching mechanisms 22 a and 22 b.

In the above-described heating main operation, like heating only operation, the control unit 19 performs control to fix the opening degree of the liquid-pressure adjustment expansion valve 26 in a fully opened state. Thus, the opening degree of the refrigerant return expansion valve 44 is brought into a fully closed state to inhibit the refrigerant from flowing to the refrigerant return pipe 41.

Operation with Leakage of Refrigerant

The operation of the air conditioner 1 when the refrigerant leaks is described next with reference to FIGS. 9 to 11. FIG. 11 is a flowchart of an operation when a refrigerant leaks in the air conditioner 1 according to one or more embodiments of the present invention. The operation of the air conditioner 1 which is described below is performed by the control unit 19 that controls the components of the air conditioner 1 (the outdoor unit 2, the indoor units 3 a, 3 b, 3 c, and 3 d, and the relay units 4 a, 4 b, 4 c, and 4 d) like the operation when the refrigerant does not leak.

The air conditioner 1 is provided with the refrigerant sensors 57 a, 57 b, 57 c, and 57 d serving as the refrigerant leakage detecting means as described above. When the refrigerant sensors 57 a, 57 b, 57 c, and 57 d detect leakage of the refrigerant, the indoor expansion valves 51 a, 51 b, 51 c, and 51 d and the cooling/heating switching valves 58 a, 58 b, 58 c, 58 d, 59 a, 59 b, 59 c, and 59 d are closed in accordance with the information of the refrigerant sensors 57 a, 57 b, 57 c, and 57 d. Thus, the indoor units 3 a, 3 b, 3 c, and 3 d can be isolated. Accordingly, the refrigerant can be inhibited from flowing from the refrigerant connection pipes 5 and 6 to the indoor units 3 a, 3 b, 3 c, and 3 d. That is, when the refrigerant leaks, the indoor expansion valves 51 a, 51 b, 51 c, and 51 d are used also as liquid-side shutoff valves, the cooling/heating switching valves 58 a, 58 b, 58 c, 58 d, 59 a, 59 b, 59 c, and 59 d are used also as gas-side shutoff valves, and these valves are closed, thereby providing a refrigerant shutoff function when the refrigerant leaks from the indoor units 3 a, 3 b, 3 c, and 3 d.

To be specific, when the refrigerant sensors 57 a, 57 b, 57 c, and 57 d detect leakage of the refrigerant (step ST1), the control unit 19 closes the indoor expansion valves 51 a, 51 b, 51 c, and 51 d and the cooling/heating switching valves 58 a, 58 b, 58 c, 58 d, 59 a, 59 b, 59 c, and 59 d (step ST4). In addition, when leakage of the refrigerant is detected in step ST1, an alarm may be given (step ST2). Further, before the indoor expansion valves 51 a, 51 b, 51 c, and 51 d and the cooling/heating switching valves 58 a, 58 b, 58 c, 58 d, 59 a, 59 b, 59 c, and 59 d are closed, the compressor 21 may be stopped (step ST3) to suppress an excessive increase in the pressure of the refrigerant.

In this way, the indoor expansion valves 51 a, 51 b, 51 c, and 51 d and the cooling/heating switching valves 58 a, 58 b, 58 c, 58 d, 59 a, 59 b, 59 c, and 59 d are closed in accordance with the information of the refrigerant sensors 57 a, 57 b, 57 c, and 57 d serving as the refrigerant leakage detecting means when the refrigerant leaks. Thus, the refrigerant is inhibited from flowing from the refrigerant connection pipes 5 and 6 to the indoor units 3 a, 3 b, 3 c, and 3 d, and increase in concentration of the refrigerant in the air-conditioning target spaces can be suppressed.

Features

The air conditioner 1 and the indoor units 3 a, 3 b, 3 c, and 3 d used for the air conditioner 1 according to one or more embodiments have the following features.

Like the air conditioner 1 and the indoor units 3 a and 3 b used for the air conditioner 1 according to one or more embodiments, the air conditioner 1 and the indoor units 3 a, 3 b, 3 c, and 3 d used for the air conditioner 1 according to one or more embodiments also have leakage of the refrigerant from the brazing portions 82 a, 82 b, 82 c, and 82 d brazing the indoor expansion valves 51 a, 51 b, 51 c, and 51 d and the connection-side indoor liquid-refrigerant pipes 72 a, 72 b, 72 c, and 72 d when the indoor expansion valves 51 a, 51 b, 51 c, and 51 d are used also as the shutoff valves on the liquid sides of the indoor units 3 a, 3 b, 3 c, and 3 d.

In this case, like the air conditioner 1 and the indoor units 3 a and 3 b used for the air conditioner 1 according to one or more embodiments, leakage of the refrigerant from the brazing portions 82 a, 82 b, 82 c, and 82 d is reduced by providing coating materials 11 a, 11 b, 11 c, and 11 d at the brazing portions 82 a, 82 b, 82 c, and 82 d.

Accordingly, like the air conditioner 1 and the indoor units 3 a and 3 b used for the air conditioner 1 according to one or more embodiments, the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor units 3 a, 3 b, 3 c, and 3 d can be added while the increase in the cost and the sizes of the indoor units 3 a, 3 b, 3 c, and 3 d due to the provision of the shutoff valves on the liquid sides of the indoor units 3 a, 3 b, 3 c, and 3 d is reduced as much as possible.

In particular, as described above, the cooling/heating switching valves 58 a, 58 b, 58 c, 58 d, 59 a, 59 b, 59 c, and 59 d of the relay units 4 a, 4 b, 4 c, and 4 d used for individually switching the operating states of the indoor units 3 a, 3 b, 3 c, and 3 d (that is, the states in which the indoor heat exchangers 52 a, 52 b, 52 c, and 52 d function as the evaporators of the refrigerant and function as the radiators of the refrigerant) are used also as the gas-side shutoff valves. As long as the cooling/heating switching valves 58 a, 58 b, 58 c, 58 d, 59 a, 59 b, 59 c, and 59 d can be used also as the shutoff valves on the gas sides of the indoor units 3 a, 3 b, 3 c, and 3 d, the increase in the cost and the sizes of the indoor units 3 a, 3 b, 3 c, and 3 d can be suppressed by that amount.

Accordingly, the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor units 3 a, 3 b, 3 c, and 3 d can be added while the increase in the cost and the sizes of the indoor units 3 a, 3 b, 3 c, and 3 d due to the provision of the shutoff valves on the gas sides of the indoor units 3 a, 3 b, 3 c, and 3 d is reduced as much as possible.

Since the outdoor unit 2 includes the liquid-pressure adjustment expansion valve 26 like the air conditioner 1 according to one or more embodiments, the two-phase refrigerant feed of decompressing the refrigerant to be brought into the gas-liquid two-phase state in the outdoor unit 2 and then sending the refrigerant to the indoor units 3 a, 3 b, 3 c, and 3 d via the liquid-refrigerant connection pipe 5 is performed. Accordingly, like the air conditioner 1 according to one or more embodiments, even in the case where the two-phase refrigerant feed is not sufficient for the countermeasure to leakage of the refrigerant, the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor units 3 a, 3 b, 3 c, and 3 d can be added while the increase in the cost and the sizes of the indoor units 3 a, 3 b, 3 c, and 3 d due to the provision of the shutoff valves on the liquid sides of the indoor units 3 a, 3 b, 3 c, and 3 d is reduced as much as possible. The addition of the refrigerant shutoff function makes the countermeasure to leakage of the refrigerant sufficient.

First Modification

In one or more embodiments, only the indoor expansion valves 51 a, 51 b, 51 c, and 51 d are provided in the indoor liquid-refrigerant pipes 53 a, 53 b, 53 c, and 53 d as illustrated in FIG. 10 in the indoor units 3 a, 3 b, 3 c, and 3 d arranged in the air-conditioning target spaces. In addition, filters 73 a, 73 b, 73 c, and 73 d for reducing inflow of foreign substances and so forth to the indoor expansion valves 51 a, 51 b, 51 c, and 51 d may be provided in the connection-side indoor liquid-refrigerant pipes 72 a, 72 b, 72 c, and 72 d as illustrated in FIG. 12 in the indoor units 3 a, 3 b, 3 c, and 3 d. The filters 73 a, 73 b, 73 c, and 73 d are also connected to the connection-side indoor liquid-refrigerant pipes 72 a, 72 b, 72 c, and 72 d by brazing. The connection-side indoor liquid-refrigerant pipes 72 a, 72 b, 72 c, and 72 d include first connection-side indoor liquid-refrigerant pipes 74 a, 74 b, 74 c, and 74 d connected to the indoor expansion valves 51 a, 51 b, 51 c, and 51 d, and second connection-side indoor liquid-refrigerant pipes 75 a, 75 b, 75 c, and 75 d connected to the liquid-refrigerant connection pipe 5 (in this case, the branch pipe portions 5 aa, 5 bb, 5 cc, and 5 dd). In addition, the filters 73 a, 73 b, 73 c, and 73 d are connected between the first connection-side indoor liquid-refrigerant pipes 74 a, 74 b, 74 c, and 74 d and the second connection-side indoor liquid-refrigerant pipes 75 a, 75 b, 75 c, and 75 d. The filters 73 a, 73 b, 73 c, and 73 d are connected to the first connection-side indoor liquid-refrigerant pipes 74 a, 74 b, 74 c, and 74 d and the second connection-side indoor liquid-refrigerant pipes 75 a, 75 b, 75 c, and 75 d by brazing (the brazing portions are referred to as brazing portions 85 a, 85 b, 85 c, 85 d, 86 a, 86 b, 86 c, and 86 d). Due to this, the brazing portions 85 a, 85 b, 85 c, 85 d, 86 a, 86 b, 86 c, and 86 d may corrode and the refrigerant may leak from the corroding portions. This makes difficult to use the indoor expansion valves 51 a, 51 b, 51 c, and 51 d also as the shutoff valves on the liquid sides of the indoor units 3 a, 3 b, 3 c, and 3 d, like the brazing portions 85 a, 85 b, 86 a, and 86 b of the indoor units 3 a and 3 b according to one or more embodiments.

To address this, as illustrated in FIG. 12, the brazing portions 85 a, 85 b, 85 c, 85 d, 86 a, 86 b, 86 c, and 86 d brazing the filters 73 a, 73 b, 73 c, and 73 d with the first connection-side indoor liquid-refrigerant pipes 74 a, 74 b, 74 c, and 74 d and the second connection-side indoor liquid-refrigerant pipes 75 a, 75 b, 75 c, and 75 d are also provided with coating materials 11 a, 11 b, 11 c, 11 d, 12 a, 12 b, 12 c, and 12 d. The first connection-side indoor liquid-refrigerant pipes 74 a, 74 b, 74 c, and 74 d including the brazing portions 82 a, 82 b, 82 c, and 82 d and the brazing portions 85 a, 85 b, 85 c, and 85 d are provided with the coating materials 11 a, 11 b, 11 c, and 11 d. The second connection-side indoor liquid-refrigerant pipes 75 a, 75 b, 75 c, and 75 d including the brazing portions 86 a, 86 b, 86 c, and 86 d and the brazing portions 83 aa, 83 bb, 83 cc, and 83 dd are provided with coating materials 12 a, 12 b, 12 c, and 12 d. When the second connection-side indoor liquid-refrigerant pipes 75 a, 75 b, 75 c, and 75 d are directly connected to the liquid-refrigerant connection pipe 5 (in this case, the branch pipe portions 5 aa, 5 bb, 5 cc, and 5 dd) by brazing, the coating materials 12 a, 12 b, 12 c, and 12 d may be provided to include the brazing portions brazing the second connection-side indoor liquid-refrigerant pipes 75 a, 75 b, 75 c, and 75 d and the liquid-refrigerant connection pipe 5 (in this case, the branch pipe portions 5 aa, 5 bb, 5 cc, and 5 dd). The way of providing the coating materials is not limited to the above-described way like the indoor units 3 a and 3 b according to one or more embodiments. Accordingly, leakage of the refrigerant from the brazing portions 85 a, 85 b, 85 c, 85 d, 86 a, 86 b, 86 c, and 86 d brazing the filters 73 a, 73 b, 73 c, and 73 d with the first connection-side indoor liquid-refrigerant pipes 74 a, 74 b, 74 c, and 74 d and the second connection-side indoor liquid-refrigerant pipes 75 a, 75 b, 75 c, and 75 d is reduced, so that the indoor expansion valves 51 a, 51 b, 51 c, and 51 d can be used also as the shutoff valves on the liquid sides of the indoor units 3 a, 3 b, 3 c, and 3 d.

Even in the case where the filters 73 a, 73 b, 73 c, and 73 d are provided in the connection-side indoor liquid-refrigerant pipes 72 a, 72 b, 72 c, and 72 d, the refrigerant shutoff function for the situation in which the refrigerant leaks from the indoor units 3 a, 3 b, 3 c, and 3 d can be added while the increase in the cost and the sizes of the indoor units 3 a, 3 b, 3 c, and 3 d due to the provision of the shutoff valves on the liquid sides of the indoor units 3 a, 3 b, 3 c, and 3 d is reduced as much as possible.

Second Modification

In the external shutoff valve units 4 a, 4 b, 4 c, and 4 d, the cooling/heating switching valves 58 a, 58 b, 58 c, 58 d, 59 a, 59 b, 59 c, and 59 d serving as the gas-side shutoff valves are connected to the gas connection pipes 62 a, 62 b, 62 c, and 62 d connected to the gas-refrigerant connection pipe 6 (the indoor-side high-pressure gas connection pipes 66 a, 66 b, 66 c, and 66 d, the outdoor-side high-pressure gas connection pipes 67 a, 67 b, 67 c, and 67 d, the indoor-side low-pressure gas connection pipes 68 a, 68 b, 68 c, and 68 d, and the outdoor-side low-pressure gas connection pipes 69 a, 69 b, 69 c, and 69 d) by brazing. Due to this, the brazing portions 92 a, 92 b, 92 c, and 92 d brazing the first cooling/heating switching valves 58 a, 58 b, 58 c, and 58 d and the outdoor-side high-pressure gas connection pipes 67 a, 67 b, 67 c, and 67 d may corrode and the refrigerant may leak from the corroding portions. In addition, the brazing portions 94 a, 94 b, 94 c, and 94 d brazing the second cooling/heating switching valves 59 a, 59 b, 59 c, and 59 d and the outdoor-side high-pressure gas connection pipes 69 a, 69 b, 69 c, and 69 d may corrode and the refrigerant may leak from the corroding portions. In the above-described embodiments, however, the relay units 4 a, 4 b, 4 c, and 4 d are arranged outside the air-conditioning target spaces. Hence, even when the refrigerant leaks from the brazing portions 92 a, 92 b, 92 c, 92 d, 94 a, 94 b, 94 c, and 94 d, the refrigerant hardly leaks to the air-conditioning target spaces. In contrast, when the relay units 4 a, 4 b, 4 c, and 4 d are arranged in the air-conditioning target spaces together with the indoor units 3 a, 3 b, 3 c, and 3 d, if the refrigerant leaks from the brazing portions 92 a, 92 b, 92 c, 92 d, 94 a, 94 b, 94 c, and 94 d, the refrigerant is continuously supplied from the gas-refrigerant connection pipe 6 to the brazing portions 92 a, 92 b, 92 c, 92 d, 94 a, 94 b, 94 c, and 94 d, and the refrigerant may continuously leak from the external shutoff valve units 4 a, 4 b, 4 c, and 4 d to the air-conditioning target spaces although the cooling/heating switching valves 58 a, 58 b, 58 c, 58 d, 59 a, 59 b, 59 c, and 59 d are closed. Thus, it is required to reduce leakage of the refrigerant from the brazing portions 92 a, 92 b, 92 c, 92 d, 94 a, 94 b, 94 c, and 94 d.

To address this, as illustrated in FIG. 13, the brazing portions 92 a, 92 b, 92 c, and 92 d brazing the first cooling/heating switching valves 58 a, 58 b, 58 c, and 58 d and the outdoor-side high-pressure gas connection pipes 67 a, 67 b, 67 c, and 67 d are also provided with coating materials 13 a, 13 b, 13 c, and 13 d. In addition, the brazing portions 94 a, 94 b, 94 c, and 94 d brazing the second cooling/heating switching valves 59 a, 59 b, 59 c, and 59 d and the outdoor-side low-pressure gas connection pipes 69 a, 69 b, 69 c, and 69 d are also provided with coating materials 14 a, 14 b, 14 c, and 14 d. The coating materials 13 a, 13 b, 13 c, 13 d, 14 a, 14 b, 14 c, and 14 d may be also provided at only the brazing portions 92 a, 92 b, 92 c, 92 d, 94 a, 94 b, 94 c, and 94 d, or may be also provided at a portion other than the brazing portions 92 a, 92 b, 92 c, 92 d, 94 a, 94 b, 94 c, and 94 d. For example, as illustrated in FIG. 13, the coating materials 13 a, 13 b, 13 c, and 13 d may be provided in a range from the first cooling/heating switching valves 58 a, 58 b, 58 c, and 58 d to the pipe joint portions 96 a, 96 b, 96 c, and 96 d of the outdoor-side high-pressure gas connection pipes 67 a, 67 b, 67 c, and 67 d (that is, so as to include the brazing portions 92 a, 92 b, 92 c, and 92 d and the brazing portions 96 aa, 96 bb, 96 cc, and 96 dd). When the outdoor-side high-pressure gas connection pipes 67 a, 67 b, 67 c, and 67 d are directly connected to the gas-refrigerant connection pipe 6 (in this case, the first branch pipe portions 7 a, 7 d, 7 c, and 7 d of the high/low-pressure gas-refrigerant connection pipe 7) by brazing, the coating materials 13 a, 13 b, 13 c, and 13 d may be provided in a range from the first cooling/heating switching valves 58 a, 58 b, 58 c, and 58 d to the brazing portions brazing the outdoor-side gas connection pipes 67 a, 67 b, 67 c, and 67 d and the gas-refrigerant connection pipe 6 (in this case, the first branch pipe portions 7 a, 7 b, 7 c, and 7 d of the high/low-pressure gas-refrigerant connection pipe 7). The coating materials 14 a, 14 b, 14 c, and 14 d may be provided in a range from the second cooling/heating switching valves 59 a, 59 b, 59 c, and 59 d to the pipe joint portions 97 a, 97 b, 97 c, and 97 d of the outdoor-side low-pressure gas connection pipes 69 a, 69 b, 69 c, and 69 d (that is, so as to include the brazing portions 94 a, 94 b, 94 c, and 94 d and the brazing portions 97 aa, 97 bb, 97 cc, and 97 dd). When the outdoor-side low-pressure gas connection pipes 69 a, 69 b, 69 c, and 69 d are directly connected to the gas-refrigerant connection pipe 6 (in this case, the branch pipe portions 8 a, 8 b, 8 c, and 8 d of the low-pressure gas-refrigerant connection pipe 8) by brazing, the coating materials 14 a, 14 b, 14 c, and 14 d may be provided in a range from the second cooling/heating switching valves 59 a, 59 b, 59 c, and 59 d to the brazing portions brazing the outdoor-side low-pressure gas connection pipes 69 a, 69 b, 69 c, and 69 d and the gas-refrigerant connection pipe 6 (in this case, the branch pipe portions 8 a, 8 b, 8 c, and 8 d of the low-pressure gas-refrigerant connection pipe 8). Accordingly, leakage of the refrigerant from the brazing portions 92 a, 92 b, 92 c, and 92 d brazing the first cooling/heating switching valves 58 a, 58 b, 58 c, and 58 d and the outdoor-side high-pressure gas connection pipes 67 a, 67 b, 67 c, and 67 d is reduced, leakage of the refrigerant from the brazing portions 94 a, 94 b, 94 c, and 94 d brazing the second cooling/heating switching valves 59 a, 59 b, 59 c, and 59 d and the outdoor-side low-pressure gas connection pipes 69 a, 69 b, 69 c, and 69 d is reduced, and hence the relay units 4 a, 4 b, 4 c, and 4 d can be arranged in the air-conditioning target spaces together with the indoor units 3 a, 3 b, 3 c, and 3 d. Referring to FIG. 13, in the configuration of the above-described embodiments (see FIG. 10) without the filters 73 a, 73 b, 73 c, and 73 d, the brazing portions 92 a, 92 b, 92 c, and 92 d brazing the first cooling/heating switching valves 58 a, 58 b, 58 c, and 58 d and the outdoor-side high-pressure gas connection pipes 67 a, 67 b, 67 c, and 67 d as well as the brazing portions 94 a, 94 b, 94 c, and 94 d brazing the second cooling/heating switching valves 59 a, 59 b, 59 c, and 59 d and the outdoor-side low-pressure gas connection pipes 69 a, 69 b, 69 c, and 69 d are provided with the coating materials 13 a, 13 b, 13 c, 13 d, 14 a, 14 b, 14 c, and 14 d; however, it is not limited to the above. For example, in the configuration of the above-described first modification (see FIG. 12) with the filters 73 a, 73 b, 73 c, and 73 d, the brazing portions 92 a, 92 b, 92 c, and 92 d brazing the first cooling/heating switching valves 58 a, 58 b, 58 c, and 58 d and the outdoor-side high-pressure gas connection pipes 67 a, 67 b, 67 c, and 67 d as well as the brazing portions 94 a, 94 b, 94 c, and 94 d brazing the second cooling/heating switching valves 59 a, 59 b, 59 c, and 59 d and the outdoor-side low-pressure gas connection pipes 69 a, 69 b, 69 c, and 69 d may be provided with the coating materials 13 a, 13 b, 13 c, 13 d, 14 a, 14 b, 14 c, and 14 d.

Accordingly, the degree of freedom is ensured for arrangement of the relay units 4 a, 4 b, 4 c, and 4 d.

Third Modification

In the above-described embodiments, as illustrated in FIG. 11, when the refrigerant sensors 57 a, 57 b, 57 c, and 57 d detect leakage of the refrigerant, all the indoor expansion valves 51 a, 51 b, 51 c, and 51 d and the cooling/heating switching valves 58 a, 58 b, 58 c, 58 d, 59 a, 59 b, 59 c, and 59 d are closed and the compressor 21 is stopped in accordance with the information of the refrigerant sensors 57 a, 57 b, 57 c, and 57 d. Accordingly, the circulation of the refrigerant in the refrigerant circuit 10 is stopped, and the cooling operation or heating operation is stopped not only in the indoor unit in which the refrigerant leaks but also in the indoor unit in which the refrigerant does not leak.

However, it is desirable that only the indoor unit in which the refrigerant leaks is isolated whereas the indoor unit in which the refrigerant does not leak can continue cooling operation or heating operation.

As illustrated in FIG. 14, when the refrigerant sensors 57 a, 57 b, 57 c, and 57 d detect leakage of the refrigerant (step ST1), the control unit 19 closes only the indoor expansion valve and the cooling/heating switching valve corresponding to the indoor unit in which the refrigerant leaks among the plurality of indoor units 3 a, 3 b, 3 c, and 3 d (step ST5). Then, by continuing the circulation of the refrigerant in the refrigerant circuit 10 without stopping the compressor 21, the cooling operation or heating operation of the indoor unit in which the refrigerant does not leak is continued (step ST6).

When the refrigerant leaks from the indoor units 3 a, 3 b, 3 c, and 3 d, only the indoor unit in which the refrigerant leaks is isolated whereas the indoor unit in which the refrigerant does not leak can continue the operation.

Fourth Modification

In the above-described embodiments, the relay units 4 a, 4 b, 4 c, and 4 d respectively corresponding to the indoor units 3 a, 3 b, 3 c, and 3 d are provided; however, it is not limited thereto. For example, a relay unit may be collectively constituted of all the relay units 4 a, 4 b, 4 c, and 4 d, or some of the relay units 4 a, 4 b, 4 c, and 4 d.

INDUSTRIAL APPLICABILITY

The present invention can be widely applied to an air conditioner configured such that an outdoor unit and an indoor unit arranged in an air-conditioning target space are connected to each other via a liquid-refrigerant connection pipe and a gas-refrigerant connection pipe, and an indoor unit used for the air conditioner.

REFERENCE SIGNS LIST

1 air conditioner

2 outdoor unit

3 a, 3 b, 3 c, 3 d indoor unit

4 a, 4 b, 4 c, 4 d external shutoff valve unit, relay unit

5 liquid-refrigerant connection pipe

6 gas-refrigerant connection pipe

11 a, 11 b, 11 c, 11 d coating material

12 a, 12 b, 12 c, 12 d coating material

13 a, 13 b, 13 c, 13 d coating material

14 a, 14 b, 14 c, 14 d coating material

15 a, 15 b coating material

19 control unit

23, 23 a, 23 b outdoor heat exchanger

26 liquid-pressure adjustment expansion valve

51 a, 51 b, 51 c, 51 d indoor expansion valve

52 a, 52 b, 52 c, 52 d indoor heat exchanger

57 a, 57 b, 57 c, 57 d refrigerant sensor (refrigerant leakage detecting means)

58 a, 58 b, 58 c, 58 d gas-side shutoff valve, first cooling/heating switching valve

59 a, 59 b, 59 c, 59 d second cooling/heating switching valve (gas-side shutoff valve)

66 a, 66 b, 66 c, 66 d indoor-side gas connection pipe

67 a, 67 b, 67 c, 67 d outdoor-side gas connection pipe

68 a, 68 b, 68 c, 68 d indoor-side gas connection pipe

69 a, 69 b, 69 c, 69 d outdoor-side gas connection pipe

71 a, 71 b, 71 c, 71 d heat-exchange-side indoor liquid-refrigerant pipe

72 a, 72 b, 72 c, 72 d connection-side indoor liquid-refrigerant pipe

73 a, 73 b, 73 c, 73 d filter

74 a, 74 b, 74 c, 74 d first connection-side indoor liquid-refrigerant pipe

75 a, 75 b, 75 c, 75 d second connection-side indoor liquid-refrigerant pipe

76 a, 76 b heat-exchange-side indoor gas-refrigerant pipe

77 a, 77 b connection-side indoor gas-refrigerant pipe

82 a, 82 b, 82 c, 82 d brazing portion

85 a, 85 b, 85 c, 85 d brazing portion

86 a, 86 b, 86 c, 86 d brazing portion

88 a, 88 b brazing portion

92 a, 92 b, 92 c, 92 d brazing portion

94 a, 94 b, 94 c, 94 d brazing portion

Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims. 

1-12. (canceled)
 13. An air conditioner comprising: an outdoor unit; a liquid-refrigerant connection pipe and a gas-refrigerant connection pipe; an indoor unit that: is connected to the outdoor unit via the liquid-refrigerant connection pipe and the gas-refrigerant connection pipe, is arranged in an air-conditioning target space, and includes: an indoor heat exchanger that performs heat exchange between: a refrigerant circulated between the indoor unit and the outdoor unit via the liquid-refrigerant connection pipe and the gas-refrigerant connection pipe, and air sent to the air-conditioning target space; an indoor expansion valve that decompresses the refrigerant; a heat-exchange-side indoor liquid-refrigerant pipe that connects a liquid side of the indoor heat exchanger to the indoor expansion valve; and a connection-side indoor liquid-refrigerant pipe that connects the indoor expansion valve to the liquid-refrigerant connection pipe; a gas-side shutoff valve that is connected to a gas side of the indoor heat exchanger; a refrigerant sensor that detects leakage of the refrigerant; and a controller, wherein the indoor expansion valve is connected to the connection-side indoor liquid-refrigerant pipe by brazing, a coating material is disposed over brazing portions of the indoor expansion valve and the connection-side indoor liquid-refrigerant, and the controller closes the indoor expansion valve and the gas-side shutoff valve based on information from the refrigerant sensor when leakage of the refrigerant is detected.
 14. The air conditioner according to claim 13, wherein the connection-side indoor liquid-refrigerant pipe includes: a first connection-side indoor liquid-refrigerant pipe connected to the indoor expansion valve; a second connection-side indoor liquid-refrigerant pipe connected to the liquid-refrigerant connection pipe; and a filter connected, by brazing, between the first connection-side indoor liquid-refrigerant pipe and the second connection-side indoor liquid-refrigerant pipe, and the coating material is disposed over brazing portions of the filter, the first connection-side indoor liquid-refrigerant pipe, and the second connection-side indoor liquid-refrigerant pipe.
 15. The air conditioner according to claim 13, wherein the outdoor unit includes an outdoor heat exchanger and a liquid-pressure adjustment expansion valve, and when the refrigerant is sent from the outdoor heat exchanger to the indoor unit via the liquid-refrigerant connection pipe, the controller controls: the liquid-pressure adjustment expansion valve to decompress the refrigerant flowing through the liquid-refrigerant connection pipe to be brought into a gas-liquid two-phase state, and the indoor expansion valve to decompress the refrigerant decompressed by the liquid-pressure adjustment expansion valve.
 16. The air conditioner according to claim 13, further comprising: a plurality of indoor units, wherein each of the indoor units includes a corresponding gas-side shutoff valve and indoor expansion valve.
 17. The air conditioner according to claim 16 wherein the controller closes only the indoor expansion valve and the gas-side shutoff valve of the indoor units where leakage of the refrigerant is detected by the refrigerant sensor.
 18. The air conditioner according to claim 13, wherein the gas-refrigerant connection pipe includes an external shutoff valve unit including the gas-side shutoff valve.
 19. The air conditioner according to claim 18, wherein the gas-side shutoff valve is connected, by brazing, to: an indoor-side gas connection pipe that is connected to a portion of the gas-refrigerant connection pipe on a side of the indoor unit; and an outdoor-side gas connection pipe that is connected to a portion of the gas-refrigerant connection pipe on a side of the outdoor unit, and a coating material is disposed over brazing portions of the gas-side shutoff valve and the outdoor-side gas connection pipe.
 20. The air conditioner according to claim 16, wherein each of the indoor units includes a corresponding indoor heat exchanger, the gas-refrigerant connection pipe includes a relay including cooling/heating switching valves that individually switches the indoor heat exchanger of each of the plurality of indoor units between an evaporator or a radiator of the refrigerant, the cooling/heating switching valve serve as the gas-side shutoff valve, and the controller closes the indoor expansion valve and the cooling/heating switching valves where leakage of the refrigerant is detected by the refrigerant sensor.
 21. The air conditioner according to claim 20, wherein each of the cooling/heating switching valves is connected, by brazing, to: an indoor-side gas connection pipe that is connected to a portion of the gas-refrigerant connection pipe on a side of the indoor unit; and an outdoor-side gas connection pipe that is connected to a portion of the gas-refrigerant connection pipe on a side of the outdoor unit, and a coating material is disposed over brazing portions of the cooling/heating switching valves and the outdoor-side gas connection pipe.
 22. The air conditioner according to claim 13, wherein the gas-side shutoff valve is provided in the indoor unit, the indoor unit further includes: a heat-exchange-side indoor gas-refrigerant pipe that connects the gas side of the indoor heat exchanger to the gas-side shutoff valve; and a connection-side indoor gas-refrigerant pipe that connects the gas-side shutoff valve to the gas-refrigerant connection pipe, the gas-side shutoff valve is connected to the connection-side indoor gas-refrigerant pipe by brazing, and a coating material is disposed over brazing portions of the gas-side shutoff valve and the connection-side indoor gas-refrigerant pipe.
 23. An indoor unit connected to an outdoor unit via a liquid-refrigerant connection pipe and a gas-refrigerant connection pipe and arranged in an air-conditioning target space, the indoor unit comprising: an indoor heat exchanger that performs heat exchange between: a refrigerant circulated between the indoor unit and the outdoor unit via the liquid-refrigerant connection pipe and the gas-refrigerant connection pipe, and air sent to the air-conditioning target space; an indoor expansion valve that decompresses the refrigerant; a heat-exchange-side indoor liquid-refrigerant pipe that connects a liquid side of the indoor heat exchanger to the indoor expansion valve; and a connection-side indoor liquid-refrigerant pipe that connects the indoor expansion valve to the liquid-refrigerant connection pipe, wherein the indoor expansion valve is connected to the connection-side indoor liquid-refrigerant pipe by brazing, and a coating material is disposed over brazing portions of the indoor expansion valve and the connection-side indoor liquid-refrigerant pipe.
 24. The indoor unit according to claim 23, further comprising: a gas-side shutoff valve that is connected to a gas side of the indoor heat exchanger; a heat-exchange-side indoor gas-refrigerant pipe that connects the gas side of the indoor heat exchanger to the gas-side shutoff valve; and a connection-side indoor gas-refrigerant pipe that connects the gas-side shutoff valve to the gas-refrigerant connection pipe, wherein the gas-side shutoff valve is connected to the connection-side indoor gas-refrigerant pipe by brazing, and a coating material is disposed over brazing portions of the gas-side shutoff valve and the connection-side indoor gas-refrigerant pipe. 